B2787

Code

Generic B — Body

Keyless Entry Control Module Communication Fault

Brand: Generic

Type: B — Body

Views: UK: 9 EN: 17 RU: 13

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Page language: EN

Blown fuse or low battery voltage to the keyless entry module
Poor or corroded ground or power connector at the module
Damaged, chafed or disconnected wiring between the module and the Body Control Module (BCM) or network bus
Faulty keyless entry module (internal failure or water intrusion)
Faulty BCM or other module on the same network causing bus errors
Aftermarket alarm/immobilizer interfering with communication

Retrieve all stored DTCs and freeze frame data from all modules; note any other communication or network codes
Verify vehicle battery voltage (12.4–12.8 V at rest) and charging system operation
Inspect and check fuses related to the keyless entry module and BCM
Visually inspect the keyless module connectors, pins and harness for corrosion, pushed pins, bent pins, or water damage
Perform backprobe or voltage checks for module power and ground with ignition on and off
Check continuity/resistance of CAN and/or LIN bus wiring between module and BCM; look for shorts to battery or ground

Module supply voltage: ~11–14 V with ignition on; near battery voltage at rest
Ground continuity: low ohms to chassis ground (near 0 Ω)
CAN bus idle voltages (single-ended): CAN High ≈ 2.5–3.5 V, CAN Low ≈ 1.5–2.5 V; differential idle near 0 V and dominant state ~2 V differential
LIN bus idle: single-wire resting near battery voltage or specified by manufacturer (check service data)
Network error counters and bus load percentage from a diagnostic scan tool
Key fob RF transmission presence (requires RF sniffing tool) if passive entry issues suspected

Read and record all DTCs from all modules. Note time/date and any related network codes (U-codes).
Check battery voltage and top-up or charge if low. Verify fuses and inspect module connectors for obvious damage.
With a scan tool, attempt to communicate with the keyless entry module. If no response, observe network status and error frames.
Verify power and ground at the module connector using a multimeter. Repair any open or high-resistance connections.
Inspect and test CAN/LIN wiring between the keyless module and BCM. Use an oscilloscope or lab scope to view bus signals if available.
Wiggle and flex the wiring harness and connectors while monitoring communication to reproduce intermittent faults; repair or replace damaged harness sections.
Remove or disable any aftermarket alarm or remote systems and re-test communications.
If wiring, power and bus integrity are good and module does not respond, check for available module software updates or reprogramming procedures and reflash if advised by manufacturer.
If reprogramming is not available or fails to restore function, replace the keyless entry module and reinitialize/relearn as required (observe immobilizer/key programming procedures).
After repair, clear DTCs and road-test. Re-check all modules for return of any communication codes.