All doors will lock but only driver's side will unlock with any FOB or switch if temperature is warmer. When outside temperature cools down, problem goes away and all locks function normally. Switches appear to work fine and wiring integrity appears fine as well. This pretty much limits the issue to the BCM, although I will check some floor pan wiring as well. Because the issue seems to be related to weather/temperature, it would seem that there is expansion and contraction of a contact, although I still cannot explain how the driver's side fron door still works all the time while the others seem to 'try' to work but don't.
Pontiac Q&AAsk Your Question
2005 Pontiac Montana Question: Door locks work intermittently. Seem to be related to temperature.
Answer #1Greg's Orange Auto (14224 Answers) , Orange, CA - (714) 361-9386globalhelper August 15, 2013, 12:36Master
ck door lock and unlock relays in relay panel
Replyjprobb, August 15, 2013, 13:25Rookie
If the relay was a problem, would not all my doors be affected? My driver's side door appears to work all the time whereas the others all lock together and they all do not open either until the ambient air cools down. Is there a relay for the driver's door and then another for the rest? The relays should be located in the black box, under the hood, on the passenger side close to the firewall, so I can check them and since the locks are not working right now (too hot outside) a simple swap of relays should rule it out or prove it is the problem.
Replyglobalhelper, August 15, 2013, 14:18Master
there is unlock and lock relay next to each other. it could be door lock actuators also but they to need to be tested with a tech2 scanner.without the scanner you are stuck ck'ing verything manually.sorry but thats what needs to be done
Replyjprobb, August 15, 2013, 15:23Rookie
Oddly enough, I see nothing marked as 'lock' relay in either my fuse panel (right side dashboard) or in the box in the engine compartment. Perhaps it is marked generically?
And...maybe this further information may help...I do have an aftermarket Python remote starter installed and I wonder if a defective relay in this system might cause the issue. I had looked at the various components of that system and all wires appeared intact but I obviously never cracked open anything nor did I do any testing as I do not have the schematics for it...so much tracing would have to be done.