Code
B1524
ALFA ROMEO
B — Body
Remote unlock circuit open
Views:
UK: 3
EN: 8
RU: 4
AI status
Completed
Completed
100%
Causes
- Blown fuse protecting remote/central-locking circuit
- Open or damaged wiring between BCM/remote receiver and door lock actuator/relay
- Corroded or loose connector pins at BCM, receiver, relay or actuator
- Failed door lock actuator (open coil)
- Faulty remote receiver or BCM output driver
- Aftermarket alarm/remote or immobiliser interfering with circuit
Symptoms
- Remote/keyfob unlock does not operate doors
- Central locking unlock not working (lock may still work)
- Doors may unlock using interior switches only (or not at all)
- No audible click from door actuator when unlock command sent
- Related DTCs stored in body control or immobiliser modules
What to check
- Check for any stored codes in body control/BCM and remote receiver modules using a compatible scan tool
- Verify keyfob battery and attempt unlock repeatedly while observing for any response
- Visually inspect fuses and relays for the central locking/remote system; replace if blown
- Inspect wiring and connectors at BCM/remote receiver, door actuators and unlock relay for corrosion, damage or loose pins
- Listen for actuator or relay clicks when remote unlock is commanded
- Back-probe unlock output pin on BCM or receiver and measure for voltage when remote unlock command is sent
Signal parameters
- Battery supply (B+) present at BCM/receiver: ~12 V (key on or at rest depending on design)
- Unlock output signal: should switch between ~0 V (inactive) and near B+ (~12 V) or ground when commanded (design-dependent)
- Door lock actuator coil resistance: expected finite low-ohm value (check OEM spec) — an open (infinite) reading indicates actuator failure
- Continuity: low resistance path between BCM/receiver output and actuator/relay input when measured end-to-end
Diagnostic algorithm
- Record freeze-frame and all stored DTCs from body/BCM and related modules.
- Perform a visual inspection of fuses, relays and connectors related to central locking and remote receiver; repair any obvious damage.
- Confirm keyfob operation (LED on fob, new battery) and verify vehicle receives command using a scan tool or by observing a request LED on receiver if available.
- With helper operating the remote, back-probe the unlock output at the BCM/receiver and check for the expected voltage change when unlock is pressed.
- If no output from BCM/receiver, check the fuse supplying that module and the module supply pins for B+ and ground.
- If the BCM/receiver produces the unlock signal, trace the harness to the door actuator/relay and check continuity to the actuator input; repair any open circuit or corroded connector.
- If the actuator/relay input is receiving correct signal but actuator does not operate, measure actuator coil resistance; if open, replace actuator.
- If wiring and actuators are good but no correct output from BCM/receiver, consider module fault. Verify communications with other modules (CAN/BUS). Replace BCM/receiver only after confirming wiring and external components are good.
- Clear DTCs after repairs and confirm repeatability by cycling remote unlock several times and rescanning for codes.
Likely causes
- Open or damaged harness or connector between BCM/receiver and unlock actuator/relay
- Blown fuse or failed unlock relay
- Faulty unlock actuator coil (open circuit)
- Failed BCM or remote receiver driver output
Fault status
Status
Remote unlock circuit open — no continuity detected between control module/receiver and unlock actuator/relay.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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