Under the Hood: Trouble with lock system

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By Brad Bergholdt Tribune News Service (TNS)

I have a 2013 Ram 1500 with power locks, and a lot of other options. The problem I’m having is with the right side lock system. When you lock the doors with the key fob (and I changed the battery) sometimes but not all the time the doors lock and the alarm is set but the lock stems on both the right front and rear doors do not go down. And at other times they work as they should. But only the right front and rear doors, regardless of what you use to activate the locking procedure (fob, driver side or passenger side controls). But the alarm systems always sets. Even using remote start system the truck functions as normal; again sometimes the lock stems go down others not.

I can’t imagine it’s both lock actuators, and I’ve moved the wiring harnesses around both right and left, front and rear. I’ve considered the BCM, but am not going to do anything unless I’m sure.

Dennis, Pennsylvania

A. Your Ram’s power door locks are controlled by the Body Control Module based on inputs, as you mentioned. When requested, a lock command will be sent to all four doors via a light green wire with a dark blue stripe (circuit P-777, this wire splices/goes to all four doors). Do both the right front and right rear doors fail to lock at exactly the same time, or can each act up randomly? If they’re at random times I’d lean toward possible faulty door lock actuators. If it’s at exactly the same time, the most likely cause seems to be a faulty wiring splice (SP-1161, located in the instrument panel harness near the glove box) where these wires merge. Since the left side doors work fine, this rules out a fault with the BCM.

The best way to diagnose this is to look for BCM fault codes, using a professional grade scan tool. These circuits are monitored, and a fault is likely to set a code, which would narrow down the search area. If you’re handy and are up for a little detective work, access the wire mentioned above at either the front or rear door connector (just behind a rubber boot at the door pillar). Using a T-pin as a probe, look for a viable (brief) 12 volt signal at the wire’s connector terminal #2 as a lock request is issued. If the signal is present, the problem is within the door. If not, finding and testing the instrument panel splice would be my next recommendation (not easy).

Renewing door lock actuators, if needed, involves removing each door trim panel, and then a large metal plate. The door lock actuator is integrated with the door latch. Parts price: aftermarket is about $50-70, the OEM part lists for about $125. Labor time is 1.4 hours for the front door and 1.0 for the rear.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at bradbergholdt@gmail.com; he cannot make personal replies.
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