Tried an advanced search & not finding an actual answer... I have FSM for pin outs & wiring diagrams external to the BCM. However, I want to know about the BCM board itself. When you look at it, there are 2 honest to goodness relays soldered onto the circuit board. They appear connected to the pin outs for driving the Colum Lock (C3 pin A6 & A8) I'm just curious if they might be the power swap relays for the Column Lock?

We are getting a B2592 with key off. Key on, it actually clears to history... but we are also getting pull key wait 10 seconds every time. Already has an LMC5 installed. Pretty sure this car also had the recall as owner had the K harness in his possession...

FSM is a bit "lacking" on its diagnostics for this code. Code is set by "internal malfunction" An open or short to ground on column lock drive B circuit. I've read the section several times & still have not seen where it says which circuit is A &/or B?? I'm assuming it's the flip between polarity to drive the lock pin motor...

Anyway per FSM, Fuse is good (step 2). Power is at pin A4 connector 3 (at all times/key on/off) Step 3. Intermittent on Pin A4(step 6) - pulled pin & tightened connector. no change... Next step in the chart is 8, program rpo for a new BCM. Thanks for nothing.

So, thinking I will pull the BCM board again, at least resolder the pins on those 2 relays. I didn't really see anything amiss anywhere under the magnifier last time though...

 

Only the 97, and 98 I believe had column lock relay inside the BCM, latter years had the external column lock relay.

 

I think all manual cars have the external relay mounted above the BCM... LMC5 directions have you remove on manual cars anyway.

So... pulled the BCM board & of the two relays on the board, one had an open on the coil pins... So, I removed it, Siemens T72m5d155-12-08 number I could not find an xref on digikey or general google search. But I had a bag of Panasonic 255-1240-ND that I use to fix door modules, rated at 15a so figured what the hell.. Soldered in, back in the car. Low & behold all errors are now GONE on BCM. Sometimes persistence is not futile...

 

Good going.

 

How's the fix holding up? I have a LMC5 with brown wire mod in place. Mine started doing the same thing. Was stranded in a parking lot trying all sorts of things. I punched the BCM a few times and the error went away! Back home, I pulled the board but all the solder joints looked fine. Error message kept popping up and it could be reliably "fixed" by tapping on the BCM with a screwdriver. That's when I noticed that the relay clicks sounded different at times. Coils measured at around 240 ohms.

 

Hitting the BCM with a 25 year-old FR4 PCB and solder joints will eventually break something else If you are the adventurous sort, you can try replacing the relays. If you brick the BCM in the process....no biggie......BCMs are readily available.

 

That is true, but I wasn't banging on it with a 5lb sledge Have relays on order, but I'm going to recheck all the wiring and take voltage measurements. Really wish there was a schematic somewhere.

 

I have not seen a component level schematic for a BCM. This is as close as your will get.

 

Thanks that is super helpful. I'll check the connections on pins A6 and C15. Barring any issues there, it looks like the "Motor Drive B" relay (assuming that's a relay in the diagram) could be the culprit.

 

Relays can and do hang up. If a relay is hanging up, vibration can allow it to operate. It looks like your on the right track.

 

Removed the unlock relay and one of the legs - the one that closes the feedback circuit to pin C15 - stayed stuck on the board. Guessing that it corroded to the point where it was barely making contact, which explains why tapping the BCM fixed the issue. This area of the car did get wet a while back due to water leak, which could explain the corrosion. Need to replace the other relay as soon as it arrives. Will likely just leave it as is since the external relay that's hooked up to that one is bypassed. In the meantime, I'll toss the BCM back in later tonight to test things out!

 

Well, how did it go?

 

Hell - now I don't remember if I replaced the other relay, but I haven't experienced any issues after replacing the one that was clearly faulty.

 

Awesome, so sounds like this is worth a try after the LMC5 + brown wire mod but before getting a whole new BCM!
Did you use the same Panasonic or equivalent relays from the door lock modules?

 

Yep - Panasonic JSM1-12V. They're <$8 on Amazon right now or you can buy them in bulk on eBay for a bit less.

 

Thanks G_Loc!
I'll keep this in my back pocket for when my BCM decides it wants an early retirement...