1999 Chevy Suburban power door locks

How do they work from the passenger door switch? If ok, look for frayed / partially broken wires between the driver's door hinges. All it takes is one remaining strand of wire to be intact, but it won't be able to pass enough current to run the locks. This will affect lock and unlock operations.

If they work properly in one direction only, and from both switches, look for a pair of relays run by the Body Computer. Switch them, then see if the locks work in the other direction. If so, one of the relays has a burned contact. It could be either one. Current flows through one of two contacts in each relay. When one relay is activated, the return current flows through the relaxed contact of the other relay.

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