B1B25

Code

Generic B — Body

Rear door lock actuator circuit malfunction

Brand: Generic

Type: B — Body

Views: UK: 17 EN: 23 RU: 15

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Page language: EN

Causes

Open or short in door lock actuator wiring (power or ground)
Corroded or loose connector at actuator or harness
Failed door lock actuator (motor or internal switch)
Faulty BCM output driver or internal relay
Intermittent connection due to pin damage or water intrusion
Blown fuse or poor ground at body/chassis

Symptoms

Rear door fails to lock or unlock with key fob or inside switch
Intermittent door lock operation or only one direction works
Clicking or no sound from rear door when command given
Other door locks operate normally (isolated to rear door)
Possible related warning on body/door module or keyless entry

What to check

Scan BCM and read freeze frame / failure counts for B1B25
Verify fuse(s) for door locks are intact and seated
Visually inspect rear door harness, grommet, and connector for corrosion, damage, or water
Operate lock/unlock while probing for voltage at actuator connector
Check for voltage at BCM output with command; check ground continuity
Wiggle harness while operating lock to reproduce intermittent faults

Signal parameters

Battery voltage at actuator power pin: ~11.5–14.5 V when commanded (vehicle on or accessory as required)
Ground continuity: near 0 Ω between actuator ground and chassis ground
Actuator coil/motor resistance (typical): 2–20 Ω (varies by design) — compare to specification or identical unit
Control signal type: switched 12 V supply or low-side switching by BCM; expect switch between ~0 V and battery voltage during operation
Intermittent signals: voltage may drop or fluctuate if connector/circuit has high resistance

Diagnostic algorithm

Retrieve freeze frame and live data from BCM; confirm B1B25 is current or stored and note any related codes.
Verify fuses and relays for door lock circuit. Replace blown fuses and re-test.
With ignition on, operate lock/unlock while listening at rear door. Probe actuator connector for voltage on power and ground presence. Document readings for lock and unlock commands.
If no voltage at connector, back-probe at BCM output with partner operating lock/unlock to verify BCM output. If BCM output present but actuator not responding, suspect actuator or connector.
Inspect and clean rear door actuator connector and wiring harness (especially through door jamb grommet). Repair any damaged wires, corroded pins, or poor grounds.
Measure actuator coil/motor resistance with connector disconnected. Compare to known-good spec or known-good actuator. If out of range, replace actuator.
If actuator tests good and wiring/connector and grounds are good but no BCM output, check for BCM internal driver faults and for related communication faults. Consider BCM reprogramming or replacement per service manual.
After repairs, clear DTCs and perform full functional test (multiple lock/unlock cycles, remote and manual) and road test to confirm reliability. Re-scan for codes.

Likely causes

Corroded/loose connector at the rear door lock actuator
Failed actuator motor (common with wear or water ingress)
Open or shorted wiring between BCM and actuator
Faulty BCM output driver or internal relay (less common)

Fault status

⚠️ Status

B1B25 — Rear door lock actuator circuit malfunction detected

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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