On my 03 avalanche the rear doors won't lock with the lock switch, keyless remote or when shifting into gear, however they will unlock in all modes. Do you know what could be causing this?
Saturday, January 19th, 2013 AT 6:41 PM
There should be lock and unlock relays in the left ip fuse box, left side of dash. The relays should be the same, switch the relays, see if problem follows the relay, if so, faulty relay. I don't usually get that lucky.
Check for applicable trouble codes, because the bcm controls ground for the relays. Do you want a wiring diagram for the system?
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