B1834

Code

Other B — Body

Door Unlock Disarm Output Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 18 EN: 23 RU: 22

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Page language: EN

Causes

Open or short in the door unlock/disarm wiring harness
Corroded or loose connector at actuator, relay or BCM
Failed door unlock actuator or motor
Blown fuse or stuck/failed relay for unlock/disarm circuit
BCM output transistor (driver) failure
Water intrusion or corrosion in switch/actuator/connector

Symptoms

Door(s) do not unlock with key fob or interior unlock switch
Intermittent or no response from central locking when commanded
No clicking sound from relay or actuator when unlock command is given
Security/alarm may not disarm properly or may behave intermittently
DTC B1834 stored and lamp or message related to door lock may be present

What to check

Scan tool: read DTCs, freeze frame data and output status; attempt to command unlock/disarm from the scanner
Visual inspection of wiring, connectors, fuses, and relays for damage, corrosion or loose pins
Verify proper battery voltage and good ground at BCM and actuator grounds
Listen for relay/actuator operation while commanding unlock
Backprobe output connector to measure voltage and observe behavior when commanded
Disconnect actuator/relay and check if code clears or changes to help isolate

Signal parameters

When commanded, BCM unlock/disarm output should change state (either switch to battery voltage or to ground depending on design)
Idle state: output should be inactive (open/high-impedance or stable low current) with no abnormal voltage
Expected voltage when active: approximately battery voltage (~12 V) on a high-side output or close to 0 V on a low-side driver (varies by vehicle design)
No continuous short to ground or to battery; current draw should be limited and consistent with actuator/relay specs
When actuator is disconnected, output should not show a short-circuit current draw

Diagnostic algorithm

Confirm code and record freeze frame / related DTCs. Attempt to reproduce the symptom while monitoring.
Perform a visual inspection: check fuses, relays, connector condition and wiring harness along the door to the BCM and actuators. Repair any obvious damage.
With ignition ON, use a scan tool to command the door unlock/disarm output while probing the output pin at the BCM or the unlock relay coil. Observe voltage change and compare to expected behavior.
If no change at the BCM output, isolate by commanding and measuring at the relay/actuator connector. If output is present at BCM but not at actuator, check continuity and connectors between them.
Check for short to ground or battery: measure resistance from the unlock output wire to ground and to battery with harness disconnected. Low resistance to ground indicates short; infinite/very high resistance indicates open circuit.
Disconnect the door actuator and cycle unlock command. If the DTC clears or output behaves normally with actuator disconnected, suspect a faulty actuator or short in its harness.
Inspect and bench-test the door lock actuator or replace it if it draws excessive current or is electrically faulty.
If wiring and actuator are good but output still fails, consider relay replacement (if used) or replacement/repair of the BCM output driver. Verify BCM grounds and power supplies before replacing module.
After repair, clear DTC(s) and perform function test and road test to confirm proper operation. Re-scan to ensure code does not return.