Hi All, Well my 05 wouldn't start the other day. I Flat bedded it to my mechanic and they diagnosed it was a clutch switch. They replaced the part and showed up many many codes. The tech spent 6 hours of diagnosis and couldn't clear the codes. The brought in a Chevy dealer tech and he couldn't clear them. I was told the dealer would be able to clear. He mentioned something about the BCM as being the culprit. To my shops credit I wasn't charged a dime for their time.

Has anyone had this happen? What is the process to diagnose this module?

Thanks for your help

 

You'll probably have to have the dealer put a Tech II on it. With these cars, computer issues can cause some really strange behavior. Before you go spending too much time and money, check the condition of the battery. A marginal battery can make the car throw all kinds of codes.

 

Could be the BCM but........several members have discovered that the 2 large, blue connectors on the BCM can be the problem. They either "just get loose" because passengers' feet have pushed on them, or/and the actual pins inside one or both connectors get corroded or bent/broken.

So I suggest you carefully remove each one and inspect closely. Then if the pins look good, clean them with electrical contact cleaner and reassemble securely.


Pic of the the BCM and the 2 offending "blue" connectors: (pic courtesy of Dano523)

 

Before you replace the BCM, what were the codes? It's typical that some U codes (communications) are present which don't pose any issues.

 

Ditto on codes, since it will tell you what the problem is to begin with.

As for the BCM, before replacing it, disconnect the battery, pull all the connectors, clean them, use some dielectric grease on the connectors, then install them. The two blue ones can cause all kinds of problems, but since the red center one is how the BCM get power to begin with, it a good idea to pull and clean it as well.

Truth be told, not long again I was chasing a low voltage problem at the gauges (battery and charging system under the hood was fine) and ended up pulling my BCM out, all the fuses out, and doing a good cleaning of all the connection (even for the fuses) with spray electrical cleaner, them re-dialectical greasing all the connection points before connecting it back up with the fuse reinstalled.

As stupid as it sounds, it was the connection points of the big blue 20 amp fuse in the BCM for the GM Lan, and even the positive and negative connection points of the red center plug that was the glitch that cured the problem.


And just a FYI, make sure that your Ac box drain line is not clogged.
Part 27,


Hence the AC box sits over the BCM, and if it's drain line gets clogged, then is will end up with collected water out of the box leaking down into the BCM to cause all types of havoc isntead.

 

Great information.... I gave it to the dealer this morning before I read these possibilities. I'm calling the service writer and ask him to have his tech try these steps first before going crazy with diagnostic costs. We struck a good relationship this morning, be also is a Air Force Veteran. I knew those 4 years would pay off...