Home / DTC / B1312 — Headlamp input circuit short to positive

B1312 — Headlamp input circuit short to positive

Detailed page for trouble code B1312.

33,400codes
59brands
10,939generic
22,461specific
Reset
Code

B1312

ALFA ROMEO B — Body

Headlamp input circuit short to positive

Brand: ALFA ROMEO
Type: B — Body
Views: UK: 5 EN: 14 RU: 7
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring insulation damaged and contacting battery positive or fused feed
  • Corroded or pushed-out connector pin at headlamp or BCM
  • Water ingress in lamp connector or harness
  • Aftermarket accessory or improper bulb retrofit creating feedback
  • Shorted splice or junction where the headlamp feed and another circuit share power
  • Faulty headlamp switch or relay stuck closed

Symptoms

  • Headlamp(s) remain on or come on unexpectedly
  • Headlamps may not follow switch or automatic light commands
  • Lamp warning or master lamp indicator illuminated on dash
  • Intermittent lamp operation or flicker
  • Relevant DTC (B1312) stored in BCM

What to check

  • Read and record all stored codes and freeze/frame data with scan tool
  • Identify whether code refers to left, right or both headlamp inputs
  • Visually inspect lamp connectors, wiring harness, and nearby clips for damage, corrosion, or water
  • Check for aftermarket taps or splices on the headlamp feed circuits
  • Inspect fuses and relays related to headlamp circuits
  • Measure voltage at headlamp connector and at the BCM input with switch OFF and ON

Signal parameters

  • Expected: With headlamp switch OFF, BCM input ≈ 0 V (low). With switch ON, BCM input ≈ battery voltage (approx. 11–15 V).
  • Fault condition: Input voltage near battery voltage when switch OFF indicates short to positive/backfeed.
  • If disconnecting lamp connector removes the voltage at BCM input (goes low), short/feedback is in lamp or harness downstream of BCM.
  • If input remains high with lamp connector disconnected, short likely in wiring near BCM, relay, or inside BCM.

Diagnostic algorithm

  1. Connect diagnostic scan tool. Read and record B1312 and any related codes. Note which side (LH/RH) is affected if indicated.
  2. Turn ignition OFF. Visually inspect the affected headlamp connector, harness, and ground points for damage, corrosion, or moisture. Repair visible damage.
  3. With ignition ON and headlamp switch OFF, measure voltage at the headlamp connector pin (signal). If near battery voltage, a positive short exists.
  4. Disconnect the headlamp connector. Re-measure voltage at the BCM/input side with switch OFF: if voltage falls to 0 V, the short is in the lamp or harness; if still high, the short is upstream (relay, power splice, or BCM).
  5. Remove/inspect bulb(s) and sockets for signs of corrosion, melted contacts, or aftermarket modifications. Re-test after removing bulb.
  6. Perform a wiggle test along the harness while monitoring the signal to reproduce intermittent shorts. Isolate sections with connector separation to narrow location.
  7. If short is in harness, repair insulation or replace affected wiring/connector. If short is traced to an aftermarket tap, remove or re-route properly with fused connection.
  8. If wiring and connectors check good and input still erroneous, test related relays and power feed circuits for stuck contacts. Replace faulty relay as required.
  9. If all external wiring and components are good, follow manufacturer BCM input diagnostic procedures (bench test or replacement). Do not replace BCM without confirming wiring and connectors are good.
  10. After repair, clear codes, cycle ignition and lights, and verify normal operation and that B1312 does not return.

Likely causes

  • Damaged harness near headlamp rubbing on chassis or frame and contacting positive feed
  • Corroded lamp connector causing unintended continuity to battery feed
  • Aftermarket wiring tap for an accessory (e.g., alarm, light bar) tied into headlamp feed
  • Relay stuck closed or welded contacts supplying constant positive to input
  • Moisture inside connector creating conductive path to battery feed

Fault status

⚠️ Status
BCM detected headlamp input voltage higher than expected when input should be low (short to positive). Fault recorded and related lamp control may be disabled or behave incorrectly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

Your experience will help others
+100 karma for a short comment :)
Send to email
Code

B1312

FIAT B — Body

Headlamp input circuit short to positive

Brand: FIAT
Type: B — Body
Views: UK: 7 EN: 13 RU: 8
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring insulation damaged and contacting battery positive or fused feed
  • Corroded or pushed-out connector pin at headlamp or BCM
  • Water ingress in lamp connector or harness
  • Aftermarket accessory or improper bulb retrofit creating feedback
  • Shorted splice or junction where the headlamp feed and another circuit share power
  • Faulty headlamp switch or relay stuck closed

Symptoms

  • Headlamp(s) remain on or come on unexpectedly
  • Headlamps may not follow switch or automatic light commands
  • Lamp warning or master lamp indicator illuminated on dash
  • Intermittent lamp operation or flicker
  • Relevant DTC (B1312) stored in BCM

What to check

  • Read and record all stored codes and freeze/frame data with scan tool
  • Identify whether code refers to left, right or both headlamp inputs
  • Visually inspect lamp connectors, wiring harness, and nearby clips for damage, corrosion, or water
  • Check for aftermarket taps or splices on the headlamp feed circuits
  • Inspect fuses and relays related to headlamp circuits
  • Measure voltage at headlamp connector and at the BCM input with switch OFF and ON

Signal parameters

  • Expected: With headlamp switch OFF, BCM input ≈ 0 V (low). With switch ON, BCM input ≈ battery voltage (approx. 11–15 V).
  • Fault condition: Input voltage near battery voltage when switch OFF indicates short to positive/backfeed.
  • If disconnecting lamp connector removes the voltage at BCM input (goes low), short/feedback is in lamp or harness downstream of BCM.
  • If input remains high with lamp connector disconnected, short likely in wiring near BCM, relay, or inside BCM.

Diagnostic algorithm

  1. Connect diagnostic scan tool. Read and record B1312 and any related codes. Note which side (LH/RH) is affected if indicated.
  2. Turn ignition OFF. Visually inspect the affected headlamp connector, harness, and ground points for damage, corrosion, or moisture. Repair visible damage.
  3. With ignition ON and headlamp switch OFF, measure voltage at the headlamp connector pin (signal). If near battery voltage, a positive short exists.
  4. Disconnect the headlamp connector. Re-measure voltage at the BCM/input side with switch OFF: if voltage falls to 0 V, the short is in the lamp or harness; if still high, the short is upstream (relay, power splice, or BCM).
  5. Remove/inspect bulb(s) and sockets for signs of corrosion, melted contacts, or aftermarket modifications. Re-test after removing bulb.
  6. Perform a wiggle test along the harness while monitoring the signal to reproduce intermittent shorts. Isolate sections with connector separation to narrow location.
  7. If short is in harness, repair insulation or replace affected wiring/connector. If short is traced to an aftermarket tap, remove or re-route properly with fused connection.
  8. If wiring and connectors check good and input still erroneous, test related relays and power feed circuits for stuck contacts. Replace faulty relay as required.
  9. If all external wiring and components are good, follow manufacturer BCM input diagnostic procedures (bench test or replacement). Do not replace BCM without confirming wiring and connectors are good.
  10. After repair, clear codes, cycle ignition and lights, and verify normal operation and that B1312 does not return.

Likely causes

  • Damaged harness near headlamp rubbing on chassis or frame and contacting positive feed
  • Corroded lamp connector causing unintended continuity to battery feed
  • Aftermarket wiring tap for an accessory (e.g., alarm, light bar) tied into headlamp feed
  • Relay stuck closed or welded contacts supplying constant positive to input
  • Moisture inside connector creating conductive path to battery feed

Fault status

⚠️ Status
BCM detected headlamp input voltage higher than expected when input should be low (short to positive). Fault recorded and related lamp control may be disabled or behave incorrectly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

Your experience will help others
+100 karma for a short comment :)
Send to email
Code

B1312

HUMMER B — Body

High Side Temp Sensor Open Circuit

Brand: HUMMER
Type: B — Body
Views: UK: 6 EN: 17 RU: 17
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring insulation damaged and contacting battery positive or fused feed
  • Corroded or pushed-out connector pin at headlamp or BCM
  • Water ingress in lamp connector or harness
  • Aftermarket accessory or improper bulb retrofit creating feedback
  • Shorted splice or junction where the headlamp feed and another circuit share power
  • Faulty headlamp switch or relay stuck closed

Symptoms

  • Headlamp(s) remain on or come on unexpectedly
  • Headlamps may not follow switch or automatic light commands
  • Lamp warning or master lamp indicator illuminated on dash
  • Intermittent lamp operation or flicker
  • Relevant DTC (B1312) stored in BCM

What to check

  • Read and record all stored codes and freeze/frame data with scan tool
  • Identify whether code refers to left, right or both headlamp inputs
  • Visually inspect lamp connectors, wiring harness, and nearby clips for damage, corrosion, or water
  • Check for aftermarket taps or splices on the headlamp feed circuits
  • Inspect fuses and relays related to headlamp circuits
  • Measure voltage at headlamp connector and at the BCM input with switch OFF and ON

Signal parameters

  • Expected: With headlamp switch OFF, BCM input ≈ 0 V (low). With switch ON, BCM input ≈ battery voltage (approx. 11–15 V).
  • Fault condition: Input voltage near battery voltage when switch OFF indicates short to positive/backfeed.
  • If disconnecting lamp connector removes the voltage at BCM input (goes low), short/feedback is in lamp or harness downstream of BCM.
  • If input remains high with lamp connector disconnected, short likely in wiring near BCM, relay, or inside BCM.

Diagnostic algorithm

  1. Connect diagnostic scan tool. Read and record B1312 and any related codes. Note which side (LH/RH) is affected if indicated.
  2. Turn ignition OFF. Visually inspect the affected headlamp connector, harness, and ground points for damage, corrosion, or moisture. Repair visible damage.
  3. With ignition ON and headlamp switch OFF, measure voltage at the headlamp connector pin (signal). If near battery voltage, a positive short exists.
  4. Disconnect the headlamp connector. Re-measure voltage at the BCM/input side with switch OFF: if voltage falls to 0 V, the short is in the lamp or harness; if still high, the short is upstream (relay, power splice, or BCM).
  5. Remove/inspect bulb(s) and sockets for signs of corrosion, melted contacts, or aftermarket modifications. Re-test after removing bulb.
  6. Perform a wiggle test along the harness while monitoring the signal to reproduce intermittent shorts. Isolate sections with connector separation to narrow location.
  7. If short is in harness, repair insulation or replace affected wiring/connector. If short is traced to an aftermarket tap, remove or re-route properly with fused connection.
  8. If wiring and connectors check good and input still erroneous, test related relays and power feed circuits for stuck contacts. Replace faulty relay as required.
  9. If all external wiring and components are good, follow manufacturer BCM input diagnostic procedures (bench test or replacement). Do not replace BCM without confirming wiring and connectors are good.
  10. After repair, clear codes, cycle ignition and lights, and verify normal operation and that B1312 does not return.

Likely causes

  • Damaged harness near headlamp rubbing on chassis or frame and contacting positive feed
  • Corroded lamp connector causing unintended continuity to battery feed
  • Aftermarket wiring tap for an accessory (e.g., alarm, light bar) tied into headlamp feed
  • Relay stuck closed or welded contacts supplying constant positive to input
  • Moisture inside connector creating conductive path to battery feed

Fault status

⚠️ Status
BCM detected headlamp input voltage higher than expected when input should be low (short to positive). Fault recorded and related lamp control may be disabled or behave incorrectly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

HTML Workshop Manuals AI manual library for HUMMER Click to show available manuals 8

HUMMER 2010 Hummer H3 Alpha

HTML Manual
Hummer H3 Alpha Years: 2010 Manual in English Sections: 37,470 AI chunks: 37,470
Short description
HUMMER · Hummer H3 Alpha · 2010

HUMMER 2010 Hummer H3 Base

HTML Manual
Hummer H3 Base Years: 2010 Manual in English Sections: 37,150 AI chunks: 37,150
Short description
HUMMER · Hummer H3 Base · 2010

HUMMER 2010 Hummer H3 Base

HTML Manual
Hummer H3 Base Years: 2010 Manual in English Sections: 37,523 AI chunks: 37,523
Short description
HUMMER · Hummer H3 Base · 2010

HUMMER 2010 Hummer H3 L5-3 3.7L

HTML Manual
Hummer H3 L5-3 Years: 2010 Manual in English Sections: 14,383 AI chunks: 14,383
Short description
HUMMER · Hummer H3 L5-3 · 2010 · 3.7L

HUMMER 2010 Hummer H3 V8-5 V8-5.3L

HTML Manual
Hummer H3 V8-5 Years: 2010 Manual in English Sections: 14,606 AI chunks: 14,606
Short description
HUMMER · Hummer H3 V8-5 · 2010 · V8-5.3L

HUMMER 2010 Hummer H3T Alpha

HTML Manual
Hummer H3T Alpha Years: 2010 Manual in English Sections: 37,368 AI chunks: 37,368
Short description
HUMMER · Hummer H3T Alpha · 2010

HUMMER 2010 Hummer H3T Base

HTML Manual
Hummer H3T Base Years: 2010 Manual in English Sections: 37,048 AI chunks: 37,048
Short description
HUMMER · Hummer H3T Base · 2010

HUMMER 2010 Hummer H3T Base

HTML Manual
Hummer H3T Base Years: 2010 Manual in English Sections: 37,425 AI chunks: 37,425
Short description
HUMMER · Hummer H3T Base · 2010
Your experience will help others
+100 karma for a short comment :)
Send to email
Code

B1312

LAND ROVER B — Body

Headlight - short circuit in the battery

Brand: LAND ROVER
Type: B — Body
Views: UK: 5 EN: 13 RU: 15
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring insulation damaged and contacting battery positive or fused feed
  • Corroded or pushed-out connector pin at headlamp or BCM
  • Water ingress in lamp connector or harness
  • Aftermarket accessory or improper bulb retrofit creating feedback
  • Shorted splice or junction where the headlamp feed and another circuit share power
  • Faulty headlamp switch or relay stuck closed

Symptoms

  • Headlamp(s) remain on or come on unexpectedly
  • Headlamps may not follow switch or automatic light commands
  • Lamp warning or master lamp indicator illuminated on dash
  • Intermittent lamp operation or flicker
  • Relevant DTC (B1312) stored in BCM

What to check

  • Read and record all stored codes and freeze/frame data with scan tool
  • Identify whether code refers to left, right or both headlamp inputs
  • Visually inspect lamp connectors, wiring harness, and nearby clips for damage, corrosion, or water
  • Check for aftermarket taps or splices on the headlamp feed circuits
  • Inspect fuses and relays related to headlamp circuits
  • Measure voltage at headlamp connector and at the BCM input with switch OFF and ON

Signal parameters

  • Expected: With headlamp switch OFF, BCM input ≈ 0 V (low). With switch ON, BCM input ≈ battery voltage (approx. 11–15 V).
  • Fault condition: Input voltage near battery voltage when switch OFF indicates short to positive/backfeed.
  • If disconnecting lamp connector removes the voltage at BCM input (goes low), short/feedback is in lamp or harness downstream of BCM.
  • If input remains high with lamp connector disconnected, short likely in wiring near BCM, relay, or inside BCM.

Diagnostic algorithm

  1. Connect diagnostic scan tool. Read and record B1312 and any related codes. Note which side (LH/RH) is affected if indicated.
  2. Turn ignition OFF. Visually inspect the affected headlamp connector, harness, and ground points for damage, corrosion, or moisture. Repair visible damage.
  3. With ignition ON and headlamp switch OFF, measure voltage at the headlamp connector pin (signal). If near battery voltage, a positive short exists.
  4. Disconnect the headlamp connector. Re-measure voltage at the BCM/input side with switch OFF: if voltage falls to 0 V, the short is in the lamp or harness; if still high, the short is upstream (relay, power splice, or BCM).
  5. Remove/inspect bulb(s) and sockets for signs of corrosion, melted contacts, or aftermarket modifications. Re-test after removing bulb.
  6. Perform a wiggle test along the harness while monitoring the signal to reproduce intermittent shorts. Isolate sections with connector separation to narrow location.
  7. If short is in harness, repair insulation or replace affected wiring/connector. If short is traced to an aftermarket tap, remove or re-route properly with fused connection.
  8. If wiring and connectors check good and input still erroneous, test related relays and power feed circuits for stuck contacts. Replace faulty relay as required.
  9. If all external wiring and components are good, follow manufacturer BCM input diagnostic procedures (bench test or replacement). Do not replace BCM without confirming wiring and connectors are good.
  10. After repair, clear codes, cycle ignition and lights, and verify normal operation and that B1312 does not return.

Likely causes

  • Damaged harness near headlamp rubbing on chassis or frame and contacting positive feed
  • Corroded lamp connector causing unintended continuity to battery feed
  • Aftermarket wiring tap for an accessory (e.g., alarm, light bar) tied into headlamp feed
  • Relay stuck closed or welded contacts supplying constant positive to input
  • Moisture inside connector creating conductive path to battery feed

Fault status

⚠️ Status
BCM detected headlamp input voltage higher than expected when input should be low (short to positive). Fault recorded and related lamp control may be disabled or behave incorrectly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

HTML Workshop Manuals AI manual library for LAND ROVER Click to show available manuals 39

LAND ROVER 2018 Discovery HSE Luxury, 3.0L Eng VIN K

HTML Manual
Discovery HSE Luxury, 3.0L Eng VIN K Years: 2018 Manual in English Sections: 52,300
Short description
LAND ROVER · Discovery HSE Luxury, 3.0L Eng VIN K · 2018 · 3.0L

LAND ROVER 2018 Discovery HSE Luxury, 3.0L Eng VIN V

HTML Manual
Discovery HSE Luxury, 3.0L Eng VIN V Years: 2018 Manual in English Sections: 50,193
Short description
LAND ROVER · Discovery HSE Luxury, 3.0L Eng VIN V · 2018 · 3.0L

LAND ROVER 2018 Discovery HSE, 3.0L Eng VIN K

HTML Manual
Discovery HSE, 3.0L Eng VIN K Years: 2018 Manual in English Sections: 52,292
Short description
LAND ROVER · Discovery HSE, 3.0L Eng VIN K · 2018 · 3.0L

LAND ROVER 2018 Discovery HSE, 3.0L Eng VIN V

HTML Manual
Discovery HSE, 3.0L Eng VIN V Years: 2018 Manual in English Sections: 50,193
Short description
LAND ROVER · Discovery HSE, 3.0L Eng VIN V · 2018 · 3.0L

LAND ROVER 2018 Discovery Sport HSE

HTML Manual
Discovery Sport HSE Years: 2018 Manual in English Sections: 50,414
Short description
LAND ROVER · Discovery Sport HSE · 2018

LAND ROVER 2018 Discovery Sport HSE Luxury

HTML Manual
Discovery Sport HSE Luxury Years: 2018 Manual in English Sections: 50,419
Short description
LAND ROVER · Discovery Sport HSE Luxury · 2018

LAND ROVER 2018 Discovery Sport SE

HTML Manual
Discovery Sport SE Years: 2018 Manual in English Sections: 50,419
Short description
LAND ROVER · Discovery Sport SE · 2018

LAND ROVER 2018 Range Rover Autobiography

HTML Manual
Range Rover Autobiography Years: 2018 Manual in English Sections: 78,130
Short description
LAND ROVER · Range Rover Autobiography · 2018
Workshop Manuals

Repair manuals for LAND ROVER

3

Land Rover Defender 300Tdi — Workshop Manual (1996 model year)

Workshop Manual
Defender 300Tdi Years: 1996 Manual in English 7.5 MB
Short description

Official workshop manual for the Land Rover Defender 300Tdi (from 1996 model year). Contains specifications, adjustment, fault diagnosis and step-by-step repair and overhaul procedures for engine, transmission, axles, suspension, brakes, electrical and body. Intended for dealer workshops and trained technicians.

199,00 UAH
Contents
Key sections:
  • 01 INTRODUCTION
  • 04 GENERAL SPECIFICATION DATA
  • 05 ENGINE TUNING DATA
  • 07 GENERAL FITTING REMINDERS
  • 09 LUBRICANTS, FLUIDS AND CAPACITIES
  • 10 MAINTENANCE
  • 12 ENGINE Tdi
  • - Description and operation
  • - Fault diagnosis
  • - Adjustment
  • - Repair and overhaul procedures
  • 19 FUEL SYSTEM Tdi
Buy

Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)

Workshop Manual
Defender Years: 1999–2002 Manual in English 7.6 MB
Short description

Workshop Manual Supplement and Body Repair Manual for the Land Rover Defender. Includes general specifications, maintenance schedules, tuning data and step‑by‑step repair procedures for engine, transmission, suspension, brakes, electrical and body repairs. Covers Defender models from 1999 and 2002 model years.

199,00 UAH
Contents
Key sections:
  • 01 - INTRODUCTION
  • - Introduction
  • - Dimensions
  • - References
  • - Repairs and replacements
  • - Poisonous substances
  • - Fuel handling precautions
  • - Synthetic rubber
  • - Recommended sealants
  • - Used engine oil precautions
  • - Accessories and conversions
  • - Wheels and tyres
Buy

Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)

Workshop Manual
Manual in English Pages: 494 7.1 MB
Short description

Land Rover Range Rover Electrical Library (LRL 0453ENG). Comprehensive manual covering fuse details, earth points, system descriptions, diagnostics and connector pin-outs for electrical troubleshooting and repair. Intended for technicians and service workshops.

199,00 UAH
Contents
Key sections:
  • 1 INTRODUCTION
  • 1.1 About this document
  • 1.2 Battery voltage
  • 1.3 Electrical precautions
  • 1.4 Battery disconnecting / charging
  • 1.5 Disciplines / greases
  • 1.6 Abbreviations
  • 1.7 HeVAC, sensors abbreviations
  • 1.8 How to use this document
  • 1.9 Connector detail format
  • 1.10 Fault diagnosis
  • 1.11 Wire colour codes
Buy
Your experience will help others
+100 karma for a short comment :)
Send to email
Code

B1312

MITSUBISHI B — Body

Timeout error (TN panel open)

Brand: MITSUBISHI
Type: B — Body
Views: UK: 8 EN: 20 RU: 17
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring insulation damaged and contacting battery positive or fused feed
  • Corroded or pushed-out connector pin at headlamp or BCM
  • Water ingress in lamp connector or harness
  • Aftermarket accessory or improper bulb retrofit creating feedback
  • Shorted splice or junction where the headlamp feed and another circuit share power
  • Faulty headlamp switch or relay stuck closed

Symptoms

  • Headlamp(s) remain on or come on unexpectedly
  • Headlamps may not follow switch or automatic light commands
  • Lamp warning or master lamp indicator illuminated on dash
  • Intermittent lamp operation or flicker
  • Relevant DTC (B1312) stored in BCM

What to check

  • Read and record all stored codes and freeze/frame data with scan tool
  • Identify whether code refers to left, right or both headlamp inputs
  • Visually inspect lamp connectors, wiring harness, and nearby clips for damage, corrosion, or water
  • Check for aftermarket taps or splices on the headlamp feed circuits
  • Inspect fuses and relays related to headlamp circuits
  • Measure voltage at headlamp connector and at the BCM input with switch OFF and ON

Signal parameters

  • Expected: With headlamp switch OFF, BCM input ≈ 0 V (low). With switch ON, BCM input ≈ battery voltage (approx. 11–15 V).
  • Fault condition: Input voltage near battery voltage when switch OFF indicates short to positive/backfeed.
  • If disconnecting lamp connector removes the voltage at BCM input (goes low), short/feedback is in lamp or harness downstream of BCM.
  • If input remains high with lamp connector disconnected, short likely in wiring near BCM, relay, or inside BCM.

Diagnostic algorithm

  1. Connect diagnostic scan tool. Read and record B1312 and any related codes. Note which side (LH/RH) is affected if indicated.
  2. Turn ignition OFF. Visually inspect the affected headlamp connector, harness, and ground points for damage, corrosion, or moisture. Repair visible damage.
  3. With ignition ON and headlamp switch OFF, measure voltage at the headlamp connector pin (signal). If near battery voltage, a positive short exists.
  4. Disconnect the headlamp connector. Re-measure voltage at the BCM/input side with switch OFF: if voltage falls to 0 V, the short is in the lamp or harness; if still high, the short is upstream (relay, power splice, or BCM).
  5. Remove/inspect bulb(s) and sockets for signs of corrosion, melted contacts, or aftermarket modifications. Re-test after removing bulb.
  6. Perform a wiggle test along the harness while monitoring the signal to reproduce intermittent shorts. Isolate sections with connector separation to narrow location.
  7. If short is in harness, repair insulation or replace affected wiring/connector. If short is traced to an aftermarket tap, remove or re-route properly with fused connection.
  8. If wiring and connectors check good and input still erroneous, test related relays and power feed circuits for stuck contacts. Replace faulty relay as required.
  9. If all external wiring and components are good, follow manufacturer BCM input diagnostic procedures (bench test or replacement). Do not replace BCM without confirming wiring and connectors are good.
  10. After repair, clear codes, cycle ignition and lights, and verify normal operation and that B1312 does not return.

Likely causes

  • Damaged harness near headlamp rubbing on chassis or frame and contacting positive feed
  • Corroded lamp connector causing unintended continuity to battery feed
  • Aftermarket wiring tap for an accessory (e.g., alarm, light bar) tied into headlamp feed
  • Relay stuck closed or welded contacts supplying constant positive to input
  • Moisture inside connector creating conductive path to battery feed

Fault status

⚠️ Status
BCM detected headlamp input voltage higher than expected when input should be low (short to positive). Fault recorded and related lamp control may be disabled or behave incorrectly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

Your experience will help others
+100 karma for a short comment :)
Send to email
Code

B1312

Other B — Body

Lamp Headlamp Input Circuit Short To Battery

Brand: Other
Type: B — Body
Views: UK: 20 EN: 40 RU: 27
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring insulation damaged and contacting battery positive or fused feed
  • Corroded or pushed-out connector pin at headlamp or BCM
  • Water ingress in lamp connector or harness
  • Aftermarket accessory or improper bulb retrofit creating feedback
  • Shorted splice or junction where the headlamp feed and another circuit share power
  • Faulty headlamp switch or relay stuck closed

Symptoms

  • Headlamp(s) remain on or come on unexpectedly
  • Headlamps may not follow switch or automatic light commands
  • Lamp warning or master lamp indicator illuminated on dash
  • Intermittent lamp operation or flicker
  • Relevant DTC (B1312) stored in BCM

What to check

  • Read and record all stored codes and freeze/frame data with scan tool
  • Identify whether code refers to left, right or both headlamp inputs
  • Visually inspect lamp connectors, wiring harness, and nearby clips for damage, corrosion, or water
  • Check for aftermarket taps or splices on the headlamp feed circuits
  • Inspect fuses and relays related to headlamp circuits
  • Measure voltage at headlamp connector and at the BCM input with switch OFF and ON

Signal parameters

  • Expected: With headlamp switch OFF, BCM input ≈ 0 V (low). With switch ON, BCM input ≈ battery voltage (approx. 11–15 V).
  • Fault condition: Input voltage near battery voltage when switch OFF indicates short to positive/backfeed.
  • If disconnecting lamp connector removes the voltage at BCM input (goes low), short/feedback is in lamp or harness downstream of BCM.
  • If input remains high with lamp connector disconnected, short likely in wiring near BCM, relay, or inside BCM.

Diagnostic algorithm

  1. Connect diagnostic scan tool. Read and record B1312 and any related codes. Note which side (LH/RH) is affected if indicated.
  2. Turn ignition OFF. Visually inspect the affected headlamp connector, harness, and ground points for damage, corrosion, or moisture. Repair visible damage.
  3. With ignition ON and headlamp switch OFF, measure voltage at the headlamp connector pin (signal). If near battery voltage, a positive short exists.
  4. Disconnect the headlamp connector. Re-measure voltage at the BCM/input side with switch OFF: if voltage falls to 0 V, the short is in the lamp or harness; if still high, the short is upstream (relay, power splice, or BCM).
  5. Remove/inspect bulb(s) and sockets for signs of corrosion, melted contacts, or aftermarket modifications. Re-test after removing bulb.
  6. Perform a wiggle test along the harness while monitoring the signal to reproduce intermittent shorts. Isolate sections with connector separation to narrow location.
  7. If short is in harness, repair insulation or replace affected wiring/connector. If short is traced to an aftermarket tap, remove or re-route properly with fused connection.
  8. If wiring and connectors check good and input still erroneous, test related relays and power feed circuits for stuck contacts. Replace faulty relay as required.
  9. If all external wiring and components are good, follow manufacturer BCM input diagnostic procedures (bench test or replacement). Do not replace BCM without confirming wiring and connectors are good.
  10. After repair, clear codes, cycle ignition and lights, and verify normal operation and that B1312 does not return.

Likely causes

  • Damaged harness near headlamp rubbing on chassis or frame and contacting positive feed
  • Corroded lamp connector causing unintended continuity to battery feed
  • Aftermarket wiring tap for an accessory (e.g., alarm, light bar) tied into headlamp feed
  • Relay stuck closed or welded contacts supplying constant positive to input
  • Moisture inside connector creating conductive path to battery feed

Fault status

⚠️ Status
BCM detected headlamp input voltage higher than expected when input should be low (short to positive). Fault recorded and related lamp control may be disabled or behave incorrectly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

Workshop Manuals

Available brands with manuals

2
AUDI 11

6-speed manual gearbox 0B1, front-wheel drive — Workshop Manual (Edition 05.2014)

Workshop Manual
Years: 2008 Manual in English Pages: 187 4.9 MB
Short description

Workshop manual for the 6‑speed manual gearbox 0B1 (front‑wheel drive). Includes identification, technical data, gearbox/selector removal & installation procedures, clutch hydraulics, adjustment instructions and front differential service. Applicable to Audi A4, Audi A5 (Coupé, Cabriolet, Sportback) and Audi Q5 as referenced in the manual. Edition: 05.2014.

199,00 UAH
Contents
Key sections:
  • 00 - Technical data
  • 1 Identification
  • 1.1 Gearbox identification
  • 2 Technical data
  • 2.1 Allocation of gearbox to engine
  • 2.1.1 Allocation - Audi A4 2008 ►
  • 2.1.2 Allocation - Audi A5 Coupé 2008 ►, Audi A5 Sportback 2010 ►
  • 2.1.3 Allocation - Audi A5 Cabriolet 2009 ►
  • 2.1.4 Allocation - Audi Q5 2008 ►
  • 2.2 Capacities
  • 3 Transmission layout
  • 3.1 Transmission layout - front‑wheel drive
Buy

Audi A3 (1997) – 1.6L 4-cylinder (2‑valve) Engine Mechanical Components Service Manual (AEH, AKL, APF) – Edition 07.2002

Workshop Manual
Years: 1997 Manual in English Pages: 283 4.3 MB
Short description

Service manual for Audi A3 (1997) 1.6L 4‑cylinder (2‑valve) engines (codes AEH, AKL, APF). Includes technical data, engine removal/installation, crankshaft group, cylinder head and valve gear, lubrication, cooling and exhaust system procedures. Edition 07.2002.

199,00 UAH
Contents
Key sections:
  • 00 - Technical data ............................................................1
  • 1 Technical data ............................................................1
  • 1.1 Technical data .......................................................1
  • 1.2 Engine number .......................................................1
  • 1.3 Engine data ........................................................1
  • 10 - Removing and installing engine ..........................................3
  • 1 Removing and installing engine .........................................3
  • 1.1 Removing and installing engine ....................................3
  • 1.2 Removing - vehicles with engine codes AEH, AKL .....................4
  • 1.3 Removing - vehicles with engine code APF ..........................18
  • 1.4 Detaching engine from gearbox ...................................35
  • 1.5 Attaching engine to repair stand ................................38
Buy

AUDI A3 (2004) Workshop Manual — 2.0L FSI Turbo (4‑cyl, 4‑valve) Engine, Mechanics — Edition 03.2017

Workshop Manual
Years: 2004 Manual in English Pages: 235 3.8 MB
Short description

Official workshop manual for the Audi A3 2.0L FSI turbo engine (mechanics). Includes step‑by‑step removal/install procedures, technical data, tightening torques and diagnostic/repair instructions. Intended for professional garages and experienced technicians.

199,00 UAH
Contents
Key sections:
  • 00 - Technical data
  • 1 Engine number
  • 2 Engine data (code letters AXX, BPY, BWA, BHZ, BZC, CDL — capacity, power, torque, bore/stroke, compression, ignition)
  • 3 Safety precautions
  • 3.1 Working on the fuel system
  • 3.2 Procedure before opening high-pressure section
  • 3.3 Working on the cooling system
  • 3.4 Using testers during road test
  • 3.5 Working on the exhaust system
  • 4 General repair instructions
  • 4.1 Cleanliness rules for fuel/injection/turbo
  • 4.2 Checking fuel system for leaks
Buy

Audi A3 2004 — Electrical System (Workshop Manual, Edition 02.2018)

Workshop Manual
Years: 2004 Manual in English Pages: 150 68.2 MB
Short description

Workshop manual for the Audi A3 (2004) — Electrical system. Includes procedures for battery, starter, alternator, gauges, wipers, exterior/interior lighting and wiring. Edition 02.2018.

199,00 UAH
Contents
Key sections:
  • List of Workshop Manual Repair Groups
  • - 27 Starter, current supply, CCS
  • - 90 Gauges, instruments
  • - 92 Windscreen wash/wipe system
  • - 94 Lights, bulbs, switches - exterior
  • - 96 Lights, bulbs, switches - interior
  • - 97 Wiring
  • 27 - Starter, current supply, CCS
  • 1 Contact corrosion
  • 2 Battery
  • 2.1 Battery - general notes
  • 2.2 Maintenance-free batteries
Buy

Audi A4 / A4 Cabriolet – 4.2 l V8 (5‑valve, timing chains) – Workshop Manual (Mechanics) – Edition 04.2007

Workshop Manual
Years: 2001–2003 Manual in English Pages: 307 7.3 MB
Short description

Comprehensive workshop manual for Audi A4 (2001) and A4 Cabriolet (2003) with the 4.2 L V8, 5‑valve engine with timing chains (Engine IDs BBK/BHF). Includes step‑by‑step procedures for engine removal/installation, crankshaft and timing chain service, cylinder head/valve gear, lubrication, cooling and exhaust system repairs. Intended for professional technicians and service workshops.

199,00 UAH
Contents
Key sections:
  • 00 - Technical data
  • 1 Engine number
  • 2 Engine data (Codes: BBK / BHF; 4.163 l; 253 kW @7000 rpm; torque 410–420 Nm; bore 84.5 mm; stroke 92.8 mm; compression ratio 11.5; RON 98)
  • 3 Safety precautions
  • 4 General repair instructions (cleanliness, fuel system, contact corrosion)
  • 10 - Removing and installing engine
  • 1 Removing engine - vehicles with manual gearbox
  • 1.1 Removing engine (tools, drain fluids, remove bumper, lock carrier, disconnect wiring, fuel, coolant, A/C lines, suspension components, propshaft, exhaust, support engine on platform, lower assembly)
  • 1.2 Separating engine and gearbox (subframe removal, support sets, remove front exhaust pipes, bolt sequence)
  • 1.3 Securing engine to engine and gearbox stand (lifting tackle, VAS 6095 support)
  • 1.4 Installing engine (clutch remarks, alignment, torque values)
  • 2 Removing and installing engine - vehicles with automatic gearbox (procedure parallels manual gearbox with ATF/torque converter notes)
Buy

Audi A4 / A4 Cabriolet — Auxiliary Heater Workshop Manual (Edition 08.2004)

Workshop Manual
Years: 2001 Manual in English Pages: 259 2.0 MB
Short description

Workshop Manual for Audi A4 and A4 Cabriolet — Auxiliary Heater (Edition 08.2004). Contains self-diagnosis procedures, fault tables, electrical and fuel system checks, final control tests, CO₂ exhaust adjustment and step-by-step removal/installation and repair procedures. Intended for professional workshop use.

199,00 UAH
Contents
Key sections:
  • 01 - Self-diagnosis, electrical checks
  • 1 Auxiliary heater self-diagnosis
  • 1.1 Technical data of self-diagnosis
  • 1.2 Function
  • 1.3 Fault recognition
  • 1.4 Guided fault-finding
  • 1.5 Technical data of self-diagnosis
  • 1.6 Test requirements for self-diagnosis
  • 1.7 Safety precautions
  • 2 Self-diagnosis procedure
  • 2.1 Connecting vehicle diagnostic VAS 5051A/K-wire adapter
  • 2.1.1 Control unit identification
Buy

Audi A4 / A4 Cabriolet (1.8T 4‑cyl turbo) — Motronic Injection & Ignition System Service Manual (Edition 01.2015)

Workshop Manual
Years: 2001 Manual in English Pages: 34 851.0 KB
Short description

Service manual for Audi A4 (2001‑) and A4 Cabriolet (2003‑) with 1.8L 4‑cylinder turbo engines. Covers Motronic fuel injection and ignition systems, diagnostic and maintenance procedures. Includes technical data, removal/installation steps and system checks.

199,00 UAH
Contents
Key sections:
  • 24 - Mixture preparation - injection
  • 1 Safety precautions and rules for cleanliness
  • 1.1 General notes on self-diagnosis
  • 1.2 Safety precautions when using testers and measuring instruments during a road test
  • 1.3 Rules for cleanliness and instructions for working on fuel system
  • 1.4 Checking vacuum system
  • 2 Injection system
  • 2.1 Technical data
  • 2.2 Overview of fitting locations - injection system
  • 3 Intake manifold
  • 3.1 Exploded view - intake manifold
  • 3.2 Removing and installing intake manifold
Buy

Audi A8 (2003) — Electrical System Workshop Manual (Edition 08.2014)

Workshop Manual
Years: 2003 Manual in English Pages: 369 9.1 MB
Short description

Comprehensive workshop manual for the Audi A8 (2003) electrical system — Edition 08.2014. Covers battery, alternator, starter, instrument cluster, wiper/washer systems, exterior/interior lighting and wiring repair procedures with step-by-step illustrations. Includes diagnostic and adjustment procedures and torque/data specifications.

199,00 UAH
Contents
Key sections:
  • 27 - Starter, current supply, CCS
  • 1 Contact corrosion
  • 2 Battery
  • 2.1 Battery - general notes
  • 2.2 Maintenance-free batteries
  • 2.3 Disconnecting and connecting battery
  • 2.4 Removing and installing battery
  • - Remove luggage compartment side trim (right-side)
  • - Connect battery charger for back-up power
  • - Detach earth and positive cables, central venting hose
  • - Remove battery retainer plate and lift battery out
  • - Installation notes, adaptation via Vehicle diagnostic tester
Buy

Audi Q4 e-tron (Type F4) - Self-study Programme SSP 685

Workshop Manual
Years: 2021 Manual in English Pages: 186 82.7 MB
Short description

Official Audi Service Training self‑study programme SSP 685 for the Audi Q4 e‑tron (Type F4). Covers body, power units, power transmission, running gear, electrics & electronics, high‑voltage system, thermal management, driver assist and infotainment. Intended for internal service training and technical familiarisation; not a workshop repair manual.

199,00 UAH
Contents
Key sections:
  • Introduction
  • - Introduction to Audi Q4 e-tron
  • - Dimensions
  • Body
  • - Body structure and materials
  • - Joining techniques
  • - Securing high-voltage battery and force progression
  • - Body assembly (doors, rear lid, panoramic sunroof)
  • - Dash panel and centre console
  • Power units
  • - Technical data: rear electric motor (VX90)
  • - Technical data: front electric motor (VX89)
Buy

Audi Q8 (2018) — Electrical System Workshop Manual (Edition 05.2019)

Workshop Manual
Years: 2018 Manual in English Pages: 645 14.8 MB
Short description

Workshop manual for the Audi Q8 (2018) — Electrical System. Includes technical data, safety notes and step‑by‑step repair procedures for battery/charging, starter/alternator, lighting, washer/wiper and wiring. Edition 05.2019.

199,00 UAH
Contents
Key sections:
  • 00 - Technical data
  • 1 Safety precautions
  • 1.1 Safety precautions when working on vehicles with start/stop system
  • 1.2 Safety precautions when using testers and measuring instruments during a road test
  • 1.3 Notes on use and safety for LED headlights and Audi laser lights
  • 2 Repair notes
  • 2.1 Rules for cleanliness
  • 2.2 General notes
  • 2.3 Contact corrosion
  • 2.4 ESD (electrostatic discharge) workplace
  • 2.5 Routing and attachment of lines and wiring
  • 2.6 Identification plates
Buy

Audi Servicing Manual — 7‑Speed Dual Clutch Transmission 0CJ / 0CL / 0CK / 0DN / 0DP / 0HL (Edition 05.2018)

Workshop Manual
Years: 2008–2019 Manual in English Pages: 128 11.1 MB
Short description

Service manual for the 7‑Speed dual‑clutch (DSG) transmissions 0CJ/0CL/0CK/0DN/0DP/0HL fitted to various Audi models. Includes repair information, clutch and gearbox disassembly/assembly, mechatronic and hydraulic system procedures, seals and differential work. Edition 05.2018.

199,00 UAH
Contents
Key sections:
  • 00 - General, Technical Data
  • 1 Repair Information
  • 1.1 General Repair Information
  • 1.2 Contact Corrosion
  • 1.3 ATF Pump, Deactivating and Draining the Hydraulic Pump Reservoir
  • 2 Rules for Cleanliness when Working on DSG® Transmission
  • 30 - Clutch
  • 1 Clutch
  • 1.1 Overview - Flywheel and Dual Clutch
  • 1.2 Flywheel, Removing and Installing
  • 1.3 Dual Clutch, Removing and Installing
  • 1.4 Input Shaft Seal, Replacing
Buy
LAND ROVER 3

Land Rover Defender 300Tdi — Workshop Manual (1996 model year)

Workshop Manual
Defender 300Tdi Years: 1996 Manual in English 7.5 MB
Short description

Official workshop manual for the Land Rover Defender 300Tdi (from 1996 model year). Contains specifications, adjustment, fault diagnosis and step-by-step repair and overhaul procedures for engine, transmission, axles, suspension, brakes, electrical and body. Intended for dealer workshops and trained technicians.

199,00 UAH
Contents
Key sections:
  • 01 INTRODUCTION
  • 04 GENERAL SPECIFICATION DATA
  • 05 ENGINE TUNING DATA
  • 07 GENERAL FITTING REMINDERS
  • 09 LUBRICANTS, FLUIDS AND CAPACITIES
  • 10 MAINTENANCE
  • 12 ENGINE Tdi
  • - Description and operation
  • - Fault diagnosis
  • - Adjustment
  • - Repair and overhaul procedures
  • 19 FUEL SYSTEM Tdi
Buy

Land Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)

Workshop Manual
Defender Years: 1999–2002 Manual in English 7.6 MB
Short description

Workshop Manual Supplement and Body Repair Manual for the Land Rover Defender. Includes general specifications, maintenance schedules, tuning data and step‑by‑step repair procedures for engine, transmission, suspension, brakes, electrical and body repairs. Covers Defender models from 1999 and 2002 model years.

199,00 UAH
Contents
Key sections:
  • 01 - INTRODUCTION
  • - Introduction
  • - Dimensions
  • - References
  • - Repairs and replacements
  • - Poisonous substances
  • - Fuel handling precautions
  • - Synthetic rubber
  • - Recommended sealants
  • - Used engine oil precautions
  • - Accessories and conversions
  • - Wheels and tyres
Buy

Land Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)

Workshop Manual
Manual in English Pages: 494 7.1 MB
Short description

Land Rover Range Rover Electrical Library (LRL 0453ENG). Comprehensive manual covering fuse details, earth points, system descriptions, diagnostics and connector pin-outs for electrical troubleshooting and repair. Intended for technicians and service workshops.

199,00 UAH
Contents
Key sections:
  • 1 INTRODUCTION
  • 1.1 About this document
  • 1.2 Battery voltage
  • 1.3 Electrical precautions
  • 1.4 Battery disconnecting / charging
  • 1.5 Disciplines / greases
  • 1.6 Abbreviations
  • 1.7 HeVAC, sensors abbreviations
  • 1.8 How to use this document
  • 1.9 Connector detail format
  • 1.10 Fault diagnosis
  • 1.11 Wire colour codes
Buy
Your experience will help others
+100 karma for a short comment :)
Send to email