Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / B1020 — Load Switch

B1020 — Load Switch

Detailed page for trouble code B1020.

34,405codes
59brands
11,914generic
22,491specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

B1020

LAND ROVER B — Body

Load Switch

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

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

  1. Connect scan tool, read and record B1020 and any associated codes; clear codes and attempt to re-create to verify persistence.
  2. Identify which outputs/loads are controlled by the reported load switch from wiring diagrams or module data.
  3. Visually inspect the load switch module, connector and harness for corrosion, pin damage, heat signs or moisture; repair as needed.
  4. Verify fuses/fusible links for the circuit and replace if blown; retest.
  5. With vehicle off, measure battery voltage at the switch supply terminal and at BCM power feed; confirm good supply and battery condition.
  6. Check ground continuity from the switch/module to chassis negative; repair high resistance grounds.
  7. 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.
  8. Perform a wiggle test on connectors and harness while watching live data and commanded responses to find intermittent faults.
  9. If wiring and connectors test good but switch does not operate correctly, replace the load switch module per manufacturer's procedure.
  10. 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.
  11. 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

B1021 B1022 B1270 U0100 U0121 P0562
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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

B1020

MITSUBISHI B — Body

Air thermo sensor performance

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

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

  1. Connect scan tool, read and record B1020 and any associated codes; clear codes and attempt to re-create to verify persistence.
  2. Identify which outputs/loads are controlled by the reported load switch from wiring diagrams or module data.
  3. Visually inspect the load switch module, connector and harness for corrosion, pin damage, heat signs or moisture; repair as needed.
  4. Verify fuses/fusible links for the circuit and replace if blown; retest.
  5. With vehicle off, measure battery voltage at the switch supply terminal and at BCM power feed; confirm good supply and battery condition.
  6. Check ground continuity from the switch/module to chassis negative; repair high resistance grounds.
  7. 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.
  8. Perform a wiggle test on connectors and harness while watching live data and commanded responses to find intermittent faults.
  9. If wiring and connectors test good but switch does not operate correctly, replace the load switch module per manufacturer's procedure.
  10. 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.
  11. 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

B1021 B1022 B1270 U0100 U0121 P0562
406

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

MITSUBISHI

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .