I previously created a thread for this, but I don't know if I should continue using it or create a new one. Many of the functions that are controlled by the BCM malfunction intermittently. I'm of the opinion that, since the functions do operate at what appears to be random times, the BCM itself is OK. Several dealers, and auto electrical repairman, have also told me that BCM's rarely need to be replaced (the estimate is that only about 8% are actually defective).

The advice I'm being given is that it is likely a ground issue. Can anyone tell me how I could troubleshoot this? If not, does anyone know where I can take this to be diagnosed and resolved?

 

Here is a link to a section of the free copy of the factory service manual for the 2007 aura XE 3.5.
2007 aura XE 3.5 BCM electrical diagrams

The first diagram shows power ground and data lines for communication.

The other four diagrams illustrate the different systems which the BCM monitors and/or controls. If it was all combined in one diagram it would be unreadable as there are so many inputs and outputs. So it's broken up into different functional systems and then split out across four diagrams.
I would first review the diagrams and identify which functionalities are not behaving properly. Then see if any of them share common circuitry, including common grounds.

The comment concerning the issue being a grounding issue is most interesting, since many times, control of various circuits by the BCM and or ECM involve certain circuits being completed by the BCM closing an internal switch that connects the rest of the external circuit to ground at the BCM. This is not true for every BCM terminal, but as you look over the other four diagrams, you'll notice there are internal switches that behave just as I described above. If they go bad inside the BCM, that's that.
Remember, however, that the BCM has to have a connection to chassis ground in order to have the.appropriate pins at ground for circuit closure to ground. And it may have more than one connection from chassis ground feeding a different set of pins.

Historically, this model was known for electrical Gremlins. Unfortunately, I don't know what they were.

You might try using AI to describe the combination of functionality that doesn't work right and see if it pulls an answer out of its digital ****. Google's Gemini makes a lot of mistakes with respect to the detailed automotive information. That said some of it is right on. Just keep challenging it.

 

I appreciate your reply, and the info. I will review/study this and see if I can figure it out.

 

Here's the manual.
https://charm.li/Saturn/2007/Aura%20V6-3.5L/

 

Thank you. It is appreciated.