ImNewHere

I did a search on BCM and came up with nothing, so I wanted to know what all the BCM controls, and what are they symptoms of a bad one.

I have a 2006 HHR that has been giving me loads of trouble lately, with the CEL, traction control, and security lights on. It also had all the gauges in the DIC flatlined other than total mileage, coolant temp, and oil life. The speedometer wouldn't work, and the transmission would stay in lockup in the forward gears. It would also shift really hard, and die if I did not 2 foot it. Those symptoms would come and go, but they kept coming more and more.

I checked the codes, the service manual and a TSB led me to believe it was the C3 connector. That did not solve it, and would not make it stop doing what it was doing. I also noticed the relay for the AC clicking all the time. I finally pulled it and some fuses. They had white, ashy corrosion on them. I cleaned all of them with a brass brush and reinserted them, and now all is well, other than the coolant temperature sometimes works, but most of the time doesn't. Of course I could not get the corrosion I could see inside the thing with a bright light. I think it may have gotten drenched when the butyl patch went on it. They replaced the fan motor, and some other stuff, but did not touch the BCM.

I wonder, does that sound like it could be my problem? I am thinking of replacing it, but wanted some feedback before I do. I'm giving it a best guess based on symptoms and troubleshooting steps, but want to hear from the experts. If it were a Cummins diesel engine I could diagnose it easily, but it isn't. So, got any information that might help? Thanks.

843de

What does the BCM Control, here's a list of the major functions.....

Power Locks
Cruise Control
Power Windows
Automatic Headlamps
Anti-Theft System (VATS/Passlock)
Door lock out protection
Courtesy Lights
Interior light Dimming
Remote Start (If equipped)
RAP (Retained Aux Power)
Daytime Running Lamps
Turn Signals
Hazard Lights
Factory Alarm
Windshield Wipers

The BCM also talks to the PCM, RBCM, Airbag Control Module, and the Factory radio.

Exactly what codes came up when you pulled them/had them pulled?

ImNewHere

I got U0101 and P0700.

843de

U0101-Lost Communication with (TCM) or Transmission Control Module

P0700-Transmission Control Module Requested MIL Illumination

Sounds like at first blush, you may have an issue with the TCM itself instead of the BCM or ECM.

Going to have to read up on this, and do some searching, its ringing a bell from quite a while back.

ImNewHere

Right now there are no issues with the transmission and traction control. Those were old codes. the only thing I am experiencing now is loss of coolant temperature signal to the gauges and DIC. It does have a CEL still, which I am going to pull any new codes from when it quits raining and I am off work. Other than that the car has been running great since I wire brushed all the corrosion from the fuses.

ChevyMgr

Thermostat is the biggest culprit on the blank coolant reading.

ImNewHere

It still blows the super hot run you out air from the vents when the heat is on, and with a heat gun I still get readings between 190 and 205 sitting there.

donbrew

But, have you checked the coolant level?

When it's cold open the pressure cap and look, and also check the tank, I think the 2006 only has a surge tank? But really, physically look; digital is nice.... but.

ImNewHere

Yep, the surge tank is right where it is supposed to be. I only lost the coolant temperature signal when I cleaned the white residue from the fuses and put them back in.

Juno115

When my thermostat went bad and eventually had to be replaced I lost the temp gauge and digital readout intermittently but what I had was a thermostat that worked 90% of the time and was too slow at modulating between open and closed. This intermittent condition lasted for a few months before I finally replaced the thermostat and the problem went away.