B1836

Code

Other B — Body

Door Unlock Disarm Output Circuit Short To Battery

Brand: Other

Type: B — Body

Views: UK: 23 EN: 31 RU: 24

AI status

Completed

ready

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Page language: EN

Causes

Damaged or pinched wiring in door harness shorted to battery voltage
Corroded or pushed-back connector terminal creating a battery feed into the output
Failed door lock/unlock actuator or motor internally shorted to battery
Faulty relay or aftermarket alarm/remote start interface backfeeding power
Internal fault in BCM or module driver transistor

Symptoms

Doors unlocking or disarming without command or unable to lock
Fuse for door lock/BCM circuit blown or repeatedly blowing
Battery draining or parasitic draw related to lock circuit
DTC present and repeat after clearing
Intermittent operation of door lock/unlock

What to check

Read freeze frame and full module UIO/BCM data with scan tool; note when DTC sets
Inspect fuses and relays for the lock/BCM circuits and replace if blown
Visually inspect door harness at hinge and connectors for damage or corrosion
Disconnect door actuator/lock switch and see if code clears
Measure voltage at the unlock/disarm output with key off — should be ~0V or open; presence of +12V indicates short
Perform continuity checks between unlock output and battery positive with ignition off (isolating modules as required)

Signal parameters

Inactive output voltage: approximately 0 V (or open circuit)
Active/unlock command voltage: approximately +12 V when pulsed or switched on
Expected current draw when driving actuator: typically a few hundred mA (varies by vehicle)
Resistance to battery positive (with harness disconnected): should be open/infinite; low resistance indicates short to battery
Switching behavior: may be steady +12V if hard short, or intermittent/pulsing if module is attempting protection

Diagnostic algorithm

Retrieve and note freeze frame data and any related door/BCM codes. Attempt to reproduce symptom while monitoring live data.
Inspect fuses, relays and visible wiring for damage. Repair or replace any blown fuses and note if they blow again.
Visually inspect connectors at the affected door, body harness grommet and module grounds for corrosion, loose pins or pushed-back terminals.
With ignition off, disconnect the door unlock actuator and other load devices on the output. Clear DTC and see if it returns. If code does not return, suspect actuator or downstream wiring.
Measure voltage on the unlock/disarm output pin at the BCM with ignition off and key on. Presence of battery voltage when output should be inactive confirms short to battery.
Isolate the short by disconnecting harness sections (door connector, body harness connectors) and rechecking voltage/continuity until the shorted segment is localized.
Perform a wiggle test and flex wiring at the door hinge while monitoring the circuit to find intermittent shorts.
If wiring and actuator are good, bench-test or substitute known-good actuator. If short follows module output with harness disconnected, suspect BCM internal fault and consider module replacement or repair.
After repair, clear codes, verify proper lock/unlock operation in all modes (remote, key, interior switch) and confirm DTC does not return. Verify no parasitic draw on battery related to the circuit.

Likely causes

Wiring chafed at door hinge or harness entry point
Connector contamination or bent terminal feeding +12V into output
Aftermarket alarm/remote starter wiring tied into lock/unlock circuit incorrectly
Actuator motor shorted to battery when at rest
BCM driver stage damaged by previous short or water intrusion

Fault status

⚠️ Status

Door Unlock/Disarm output circuit shorted to battery voltage. The module detects a high voltage condition on the unlock driver when it should be inactive. May cause unintended unlocking, blown fuse, or parasitic drain.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours