Doors locking by themsleves
 

I have a 2008 LT 2.2 auto. When I start the car, the locks go crazy and lock (not unlocking) erratically by themselves. While it is going crazy, I cannot press/release the shifter button to put in gear. However, in between the madness when I am finally able to to press the button and put in gear (in any gear - even neutral)... the erratic locking stops. I know the drivers side door had water in it, as every time it rained the speaker would sound like crap, until it finally died.

Door switch? BCM? Thanks.

Do you have an aftermarket alarm or remote start installed?

Nope. Neither. Only thing aftermarket electrical wise is the stereo. The shop wired an adapter into the steering wheel to use the controls, have the backup cam show when put in reverse, etc.

And today I got a CEL and P0128 code with --- temperature on the dash. First CEL since bought new in late 2007.

Here's the problem with that...99% of aftermarket installers don't have any concept of the implications of the modifications that they make. They literally just use a test light - on/off - to determine if a circuit is usable. With modern (10+ past years) vehicles, many circuits will show 12+ volts regardless of operation; it's all diagnostic voltage. They tap into these circuits thinking it's a power source, and they the circuitry and/or module gets cooked. Before you do anything else, I would recommend isolating the aftermarket modifications from the factory circuits and then re-evaluating.

Finally fixed the weird door lock issue. Corroded/melted wire shorting out in engine bay to the trans per the techs. Got raped though as I took it to the dealership, and had a few other things done as well. ie. coolant sensor replaced to fix CEL, coolant flush, new thermostat, etc.

I do notice now that it gets warmer inside and quicker, and the coolant temp on dash goes up much quicker and higher. It never really got above ~ 195 F recently until went to dealership. When I went through the drive through car wash yesterday, it got to ~ 217 F pretty quick... then the fan kicked in (which I don't even recall the last time it came on) and the temp dropped pretty fast to about 188 F in a few mins.