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- Step 1: Confirm the symptom
- Identify exactly what’s failing: door locks (all/one side/one door), washer pump, trunk/liftgate/flipper glass
- Note if it’s constant or intermittent
- Step 2: Battery + voltage sanity check
- Make sure the battery is fully charged
- If the vehicle had a dead battery recently, jump starts, or battery replacement, re-test after stable voltage
- Step 3: Quick fuse check (do this before anything else)
- Check fuses related to:
- BCM / Fuse Box / Junction Box
- Door locks
- Washer pump
- Trunk/Liftgate release
- If a fuse is blown:
- Replace once and re-test
- If it blows again, stop and inspect for a shorted actuator/pump or wiring damage
- Check fuses related to:
- Step 4: Full vehicle scan
- Scan the whole vehicle (not only engine)
- Write down BCM codes + any network/communication codes
- Clear codes and see what returns immediately
- Step 5: Confirm BCM communication
- Verify the scan tool can connect to the BCM
- If the BCM does not communicate:
- Go straight to Step 6 and Step 7 (power/ground + connector checks)
- Step 6: Power and ground checks
- Check BCM power feeds (battery + ignition feeds if applicable)
- Check BCM grounds under load (a weak ground can pass a meter test but fail when locks/pump are commanded)
- Step 7: Connector inspection (very common cause)
- Unplug and inspect BCM/fuse box connectors for:
- Corrosion/green pins
- Moisture/water evidence
- Pushed-out pins
- Loose terminals
- Overheated/melted plastic
- Re-seat all connectors fully and ensure latches click/lock
- Unplug and inspect BCM/fuse box connectors for:
- Step 8: Rule out “single component” failures
- If only one door lock fails:
- Inspect that door’s actuator and the door-jamb wiring first (broken wires are common)
- If only washer fails:
- Confirm the washer pump isn’t seized and wiring isn’t shorted
- If only trunk/liftgate fails:
- Inspect hinge-area wiring and latch condition first
- If only one door lock fails:
- Step 9: Check for aftermarket interference
- If the vehicle has an aftermarket alarm/remote start:
- These often splice into lock circuits
- If possible, temporarily isolate/disable it for testing
- If the vehicle has an aftermarket alarm/remote start:
- Step 10: Re-test functions from multiple inputs
- Door locks: key fob + interior switch
- Washer: stalk switch
- Trunk/liftgate: button + key fob
- Confirm consistent operation (try several cycles)
- Step 11: Re-scan after testing
- Re-check BCM codes after the re-test
- If codes return immediately, note them for diagnosis
- Step 12: Programming note (important)
- If the BCM was replaced or swapped, some vehicles require vehicle programming/configuration for features to work correctly
- If still not fixed
- Contact UpFix by phone or email for the fastest help, especially if the issue happens immediately after install
This topic was modified 1 day ago by Ernest
Topic starter
Posted : 01/07/2026 10:48 am