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Home / DTC / B1509 — Hazard flasher switch circuit short to positive

B1509 — Hazard flasher switch circuit short to positive

Detailed page for trouble code B1509.

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59brands
11,914generic
22,491specific
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Code

B1509

ALFA ROMEO B — Body

Hazard flasher switch circuit short to positive

Brand: ALFA ROMEO
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring shorted to battery positive (pin-to-power contact)
  • Damaged or chafed harness near switch or BCM
  • Corroded or pushed-back connector terminal creating contact with positive
  • Faulty hazard flasher switch (internal short)
  • Body control module (BCM) input driver fault or internal short
  • Aftermarket accessories or recent repairs damaging the circuit or splice

Symptoms

  • Hazard lights may operate continuously or not operate correctly
  • Turn signals/hazard indicators may be inoperative or behave erratically
  • Warning lamp on dash related to lighting/body electronics
  • Intermittent operation dependent on harness position (wiring fault)
  • Parasitic battery drain when vehicle is off (if short is permanent)

What to check

  • Read and record all stored freeze-frame and related B/C codes from the BCM
  • Visually inspect hazard switch, wiring harness, and connectors for damage, corrosion, bends, or signs of overheating
  • Check related fuses (body/lighting) for correct rating and condition
  • Backprobe the hazard switch connector with ignition on and off to measure voltage
  • Inspect area where harness passes through bulkheads, steering column, and fuse/relay boxes for chafing
  • Disconnect the hazard switch and check for voltage on the switch feed and the switch signal pin to isolate switch vs. harness/BCM

Signal parameters

  • Expected voltage at hazard switch signal pin: ~0 V (off) or pulsed ~0–12 V when active
  • Short condition: steady ~12 V present on the signal pin when switch is off
  • Flasher rate when working: approximately 1–2 Hz (50% duty typical) at the output to lamps
  • Circuit supply voltage: battery nominal 12 V (key on & off behaviors differ; fault typically flagged with ignition on)

Diagnostic algorithm

  1. Record codes and vehicle symptom history; note if codes are permanent/stored/active. 2) Visually inspect the hazard switch, surrounding harness, and connectors for damage, moisture, or corrosion. Repair any obvious damage. 3) With ignition ON, backprobe the hazard switch connector: measure voltage on the signal terminal with switch OFF — if steady ~12 V, suspect short to positive in harness or BCM driver. 4) Disconnect the hazard switch connector. Measure if battery positive is present on the signal pin of the vehicle harness. If the harness still shows ~12 V with switch disconnected, the short is upstream (harness splice or BCM). 5) If harness is low (
  2. similar_codes([

Likely causes

  • Wiring rubbed through and contacting a 12V supply (most likely)
  • Faulty or water-damaged hazard switch (common)
  • Connector corrosion or bent terminal at switch or BCM
  • Failed BCM input driver (less common)

Fault status

⚠️ Status
Control module detected a short-to-positive on the hazard flasher switch circuit: the switch signal line is at battery positive when it should be low or pulsed. Fault remains until the input returns to expected values or is repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5 - 2.0 hours

Similar codes

B1508 B1510 B1200
89

Browse 89 ALFA ROMEO manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

ALFA ROMEO

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Code

B1509

FIAT B — Body

Hazard flasher switch circuit short to positive

Brand: FIAT
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring shorted to battery positive (pin-to-power contact)
  • Damaged or chafed harness near switch or BCM
  • Corroded or pushed-back connector terminal creating contact with positive
  • Faulty hazard flasher switch (internal short)
  • Body control module (BCM) input driver fault or internal short
  • Aftermarket accessories or recent repairs damaging the circuit or splice

Symptoms

  • Hazard lights may operate continuously or not operate correctly
  • Turn signals/hazard indicators may be inoperative or behave erratically
  • Warning lamp on dash related to lighting/body electronics
  • Intermittent operation dependent on harness position (wiring fault)
  • Parasitic battery drain when vehicle is off (if short is permanent)

What to check

  • Read and record all stored freeze-frame and related B/C codes from the BCM
  • Visually inspect hazard switch, wiring harness, and connectors for damage, corrosion, bends, or signs of overheating
  • Check related fuses (body/lighting) for correct rating and condition
  • Backprobe the hazard switch connector with ignition on and off to measure voltage
  • Inspect area where harness passes through bulkheads, steering column, and fuse/relay boxes for chafing
  • Disconnect the hazard switch and check for voltage on the switch feed and the switch signal pin to isolate switch vs. harness/BCM

Signal parameters

  • Expected voltage at hazard switch signal pin: ~0 V (off) or pulsed ~0–12 V when active
  • Short condition: steady ~12 V present on the signal pin when switch is off
  • Flasher rate when working: approximately 1–2 Hz (50% duty typical) at the output to lamps
  • Circuit supply voltage: battery nominal 12 V (key on & off behaviors differ; fault typically flagged with ignition on)

Diagnostic algorithm

  1. Record codes and vehicle symptom history; note if codes are permanent/stored/active. 2) Visually inspect the hazard switch, surrounding harness, and connectors for damage, moisture, or corrosion. Repair any obvious damage. 3) With ignition ON, backprobe the hazard switch connector: measure voltage on the signal terminal with switch OFF — if steady ~12 V, suspect short to positive in harness or BCM driver. 4) Disconnect the hazard switch connector. Measure if battery positive is present on the signal pin of the vehicle harness. If the harness still shows ~12 V with switch disconnected, the short is upstream (harness splice or BCM). 5) If harness is low (
  2. similar_codes([

Likely causes

  • Wiring rubbed through and contacting a 12V supply (most likely)
  • Faulty or water-damaged hazard switch (common)
  • Connector corrosion or bent terminal at switch or BCM
  • Failed BCM input driver (less common)

Fault status

⚠️ Status
Control module detected a short-to-positive on the hazard flasher switch circuit: the switch signal line is at battery positive when it should be low or pulsed. Fault remains until the input returns to expected values or is repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5 - 2.0 hours

Similar codes

B1508 B1510 B1200
Repair manuals

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26

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Code

B1509

MITSUBISHI B — Body

Wrong installation of ECU

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring shorted to battery positive (pin-to-power contact)
  • Damaged or chafed harness near switch or BCM
  • Corroded or pushed-back connector terminal creating contact with positive
  • Faulty hazard flasher switch (internal short)
  • Body control module (BCM) input driver fault or internal short
  • Aftermarket accessories or recent repairs damaging the circuit or splice

Symptoms

  • Hazard lights may operate continuously or not operate correctly
  • Turn signals/hazard indicators may be inoperative or behave erratically
  • Warning lamp on dash related to lighting/body electronics
  • Intermittent operation dependent on harness position (wiring fault)
  • Parasitic battery drain when vehicle is off (if short is permanent)

What to check

  • Read and record all stored freeze-frame and related B/C codes from the BCM
  • Visually inspect hazard switch, wiring harness, and connectors for damage, corrosion, bends, or signs of overheating
  • Check related fuses (body/lighting) for correct rating and condition
  • Backprobe the hazard switch connector with ignition on and off to measure voltage
  • Inspect area where harness passes through bulkheads, steering column, and fuse/relay boxes for chafing
  • Disconnect the hazard switch and check for voltage on the switch feed and the switch signal pin to isolate switch vs. harness/BCM

Signal parameters

  • Expected voltage at hazard switch signal pin: ~0 V (off) or pulsed ~0–12 V when active
  • Short condition: steady ~12 V present on the signal pin when switch is off
  • Flasher rate when working: approximately 1–2 Hz (50% duty typical) at the output to lamps
  • Circuit supply voltage: battery nominal 12 V (key on & off behaviors differ; fault typically flagged with ignition on)

Diagnostic algorithm

  1. Record codes and vehicle symptom history; note if codes are permanent/stored/active. 2) Visually inspect the hazard switch, surrounding harness, and connectors for damage, moisture, or corrosion. Repair any obvious damage. 3) With ignition ON, backprobe the hazard switch connector: measure voltage on the signal terminal with switch OFF — if steady ~12 V, suspect short to positive in harness or BCM driver. 4) Disconnect the hazard switch connector. Measure if battery positive is present on the signal pin of the vehicle harness. If the harness still shows ~12 V with switch disconnected, the short is upstream (harness splice or BCM). 5) If harness is low (
  2. similar_codes([

Likely causes

  • Wiring rubbed through and contacting a 12V supply (most likely)
  • Faulty or water-damaged hazard switch (common)
  • Connector corrosion or bent terminal at switch or BCM
  • Failed BCM input driver (less common)

Fault status

⚠️ Status
Control module detected a short-to-positive on the hazard flasher switch circuit: the switch signal line is at battery positive when it should be low or pulsed. Fault remains until the input returns to expected values or is repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5 - 2.0 hours

Similar codes

B1508 B1510 B1200
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email
Code

B1509

Other B — Body

Flash To Pass Switch Circuit Short To Battery

Brand: Other
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Wiring shorted to battery positive (pin-to-power contact)
  • Damaged or chafed harness near switch or BCM
  • Corroded or pushed-back connector terminal creating contact with positive
  • Faulty hazard flasher switch (internal short)
  • Body control module (BCM) input driver fault or internal short
  • Aftermarket accessories or recent repairs damaging the circuit or splice

Symptoms

  • Hazard lights may operate continuously or not operate correctly
  • Turn signals/hazard indicators may be inoperative or behave erratically
  • Warning lamp on dash related to lighting/body electronics
  • Intermittent operation dependent on harness position (wiring fault)
  • Parasitic battery drain when vehicle is off (if short is permanent)

What to check

  • Read and record all stored freeze-frame and related B/C codes from the BCM
  • Visually inspect hazard switch, wiring harness, and connectors for damage, corrosion, bends, or signs of overheating
  • Check related fuses (body/lighting) for correct rating and condition
  • Backprobe the hazard switch connector with ignition on and off to measure voltage
  • Inspect area where harness passes through bulkheads, steering column, and fuse/relay boxes for chafing
  • Disconnect the hazard switch and check for voltage on the switch feed and the switch signal pin to isolate switch vs. harness/BCM

Signal parameters

  • Expected voltage at hazard switch signal pin: ~0 V (off) or pulsed ~0–12 V when active
  • Short condition: steady ~12 V present on the signal pin when switch is off
  • Flasher rate when working: approximately 1–2 Hz (50% duty typical) at the output to lamps
  • Circuit supply voltage: battery nominal 12 V (key on & off behaviors differ; fault typically flagged with ignition on)

Diagnostic algorithm

  1. Record codes and vehicle symptom history; note if codes are permanent/stored/active. 2) Visually inspect the hazard switch, surrounding harness, and connectors for damage, moisture, or corrosion. Repair any obvious damage. 3) With ignition ON, backprobe the hazard switch connector: measure voltage on the signal terminal with switch OFF — if steady ~12 V, suspect short to positive in harness or BCM driver. 4) Disconnect the hazard switch connector. Measure if battery positive is present on the signal pin of the vehicle harness. If the harness still shows ~12 V with switch disconnected, the short is upstream (harness splice or BCM). 5) If harness is low (
  2. similar_codes([

Likely causes

  • Wiring rubbed through and contacting a 12V supply (most likely)
  • Faulty or water-damaged hazard switch (common)
  • Connector corrosion or bent terminal at switch or BCM
  • Failed BCM input driver (less common)

Fault status

⚠️ Status
Control module detected a short-to-positive on the hazard flasher switch circuit: the switch signal line is at battery positive when it should be low or pulsed. Fault remains until the input returns to expected values or is repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5 - 2.0 hours

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B1508 B1510 B1200
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