Code
B1020
LAND ROVER
B — Body
Load Switch
Views:
UK: 16
EN: 16
RU: 9
AI status
Completed
Completed
100%
Causes
- Failed/shorted load switch module
- Open or shorted wiring harness to the load switch
- Corroded/damaged connector or pins
- Poor battery positive supply or ground to the switch
- Blown fuse or fusible link feeding the switch
- Moisture/contamination at connector or module
Symptoms
- One or more body electrical loads inoperative (interior lights, seat heaters, auxiliary circuits, etc.)
- Intermittent operation of affected circuits
- Battery parasitic drain or fuse blowing
- Warning or message on dash about electrical system
- Related modules reporting loss of supply or communication
What to check
- Read freeze-frame and related DTCs with a quality scan tool; note affected circuits and module reporting the code
- Visually inspect the load switch module, adjacent connectors and harness for corrosion, heat damage or water ingress
- Check fuses and fusible links for the circuit(s) involved
- Measure battery voltage at the switch supply with key off and key on (should be near battery voltage)
- Check ground continuity from switch ground to chassis battery negative
- Using scan tool, command affected loads ON/OFF and observe responses
Signal parameters
- Supply (battery) voltage to load switch: ~12.0–14.5 V (key on/engine running)
- Control input: logic level (0/5/12 V) or PWM duty cycle from BCM — varies by model
- Ground resistance from switch ground to chassis:
- Closed switch resistance (when commanded on): very low (near 0 ohm)
- Current draw of protected circuit: compare measured amps to expected load specification
Diagnostic algorithm
- Connect scan tool, read and record B1020 and any associated codes; clear codes and attempt to re-create to verify persistence.
- Identify which outputs/loads are controlled by the reported load switch from wiring diagrams or module data.
- Visually inspect the load switch module, connector and harness for corrosion, pin damage, heat signs or moisture; repair as needed.
- Verify fuses/fusible links for the circuit and replace if blown; retest.
- With vehicle off, measure battery voltage at the switch supply terminal and at BCM power feed; confirm good supply and battery condition.
- Check ground continuity from the switch/module to chassis negative; repair high resistance grounds.
- With scan tool, command the specific load ON and OFF while measuring at the switch output: verify supply presence and that the switch closes (low resistance) when commanded.
- Perform a wiggle test on connectors and harness while watching live data and commanded responses to find intermittent faults.
- If wiring and connectors test good but switch does not operate correctly, replace the load switch module per manufacturer's procedure.
- If replacement does not clear fault, check BCM communication and power supplies; consider BCM reflash or replacement only after verifying wiring and load switch operation.
- After repair, clear codes and run functional tests and a road or static test to verify the fault is resolved.
Likely causes
- Failed load switch unit
- Corroded or loose connector at the switch or fusebox
- Open circuit or short in supply or ground wiring
- Blown fuse feeding the load switch
Fault status
Status
Load switch circuit fault detected—open/short/supply/ground or control/communication failure.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
Similar codes
Workshop Manuals
Repair manuals for LAND ROVER
3
Land Rover Defender 300Tdi — Workshop Manual (1996 model year)
Workshop ManualLand Rover Defender Workshop Manual Supplement & Body Repair Manual (1999 & 2002 MY)
Workshop ManualLand Rover Range Rover — Electrical Library (LRL 0453ENG, 2002)
Workshop ManualYour experience will help others
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Code
B1020
MITSUBISHI
B — Body
Air thermo sensor performance
Views:
UK: 17
EN: 23
RU: 9
AI status
Completed
Completed
100%
Causes
- Failed/shorted load switch module
- Open or shorted wiring harness to the load switch
- Corroded/damaged connector or pins
- Poor battery positive supply or ground to the switch
- Blown fuse or fusible link feeding the switch
- Moisture/contamination at connector or module
Symptoms
- One or more body electrical loads inoperative (interior lights, seat heaters, auxiliary circuits, etc.)
- Intermittent operation of affected circuits
- Battery parasitic drain or fuse blowing
- Warning or message on dash about electrical system
- Related modules reporting loss of supply or communication
What to check
- Read freeze-frame and related DTCs with a quality scan tool; note affected circuits and module reporting the code
- Visually inspect the load switch module, adjacent connectors and harness for corrosion, heat damage or water ingress
- Check fuses and fusible links for the circuit(s) involved
- Measure battery voltage at the switch supply with key off and key on (should be near battery voltage)
- Check ground continuity from switch ground to chassis battery negative
- Using scan tool, command affected loads ON/OFF and observe responses
Signal parameters
- Supply (battery) voltage to load switch: ~12.0–14.5 V (key on/engine running)
- Control input: logic level (0/5/12 V) or PWM duty cycle from BCM — varies by model
- Ground resistance from switch ground to chassis:
- Closed switch resistance (when commanded on): very low (near 0 ohm)
- Current draw of protected circuit: compare measured amps to expected load specification
Diagnostic algorithm
- Connect scan tool, read and record B1020 and any associated codes; clear codes and attempt to re-create to verify persistence.
- Identify which outputs/loads are controlled by the reported load switch from wiring diagrams or module data.
- Visually inspect the load switch module, connector and harness for corrosion, pin damage, heat signs or moisture; repair as needed.
- Verify fuses/fusible links for the circuit and replace if blown; retest.
- With vehicle off, measure battery voltage at the switch supply terminal and at BCM power feed; confirm good supply and battery condition.
- Check ground continuity from the switch/module to chassis negative; repair high resistance grounds.
- With scan tool, command the specific load ON and OFF while measuring at the switch output: verify supply presence and that the switch closes (low resistance) when commanded.
- Perform a wiggle test on connectors and harness while watching live data and commanded responses to find intermittent faults.
- If wiring and connectors test good but switch does not operate correctly, replace the load switch module per manufacturer's procedure.
- If replacement does not clear fault, check BCM communication and power supplies; consider BCM reflash or replacement only after verifying wiring and load switch operation.
- After repair, clear codes and run functional tests and a road or static test to verify the fault is resolved.
Likely causes
- Failed load switch unit
- Corroded or loose connector at the switch or fusebox
- Open circuit or short in supply or ground wiring
- Blown fuse feeding the load switch
Fault status
Status
Load switch circuit fault detected—open/short/supply/ground or control/communication failure.
Repair difficulty: Medium
Diagnostic time: 1.0 - 2.5 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email