So, I had an issue with the ABS / Traction System. Symptoms were:

• Amber check engine light
• Brake light (as if the e-brake was on) on all the time
• ABS light
• Tire pressure monitor light
• Traction control light
• Speedometer working intermittently
• Odometer working intermittently

Following this thread I was able to determine that I had two fuses blown. So, I disconnected the positive terminal from the battery and swapped out my two blown fuses. I reconnected the positive terminal, started the car and drove about an hour to my office. I was thrilled! The above symptoms were resolved (well, check engine light was still on but after a couple other trips later that light cleared itself as well)!



I stop at the gas station and turn off the key to get out and pump gas when I realize that with the key out of the ignition in my hand the engine is still running! I went ahead and stalled the engine (good thing I have a manual) and start looking around.


Here is what I can tell so far....


When I turn off the key and the engine keeps running here is what is going on:

• Engine still running
• All instruments are illuminated and working (tack, speedo, etc)
• Headlights go on (even if its light out and they weren't on before)
• Radio powers off
• Heat/AC off
• Doors unlock with key removal

When it gets like this the only thing I can do is disconnect the negative battery terminal and cut power. If I reconnect power right away I've noticed that the headlights come back on, the dash lights up, and one weird thing is all three break lights are lit up (no body is in the car pushing the breaks). If I let it sit without power for a while then reconnect the negative terminal it seems to go back to normal.


I have replaced the battery per some other posts I read that said when the battery starts going it can cause electrical malfunctions like this.


One other thing I've noticed is after I installed the brand new battery, everything seemed fine. I drove back home (about 5 min) and parked in my garage. I turned the key off and it turned of exactly as it should. Dome light comes on, doors unlock, in my mind I'm like whoo hoo its fixed. Then I open my driver door and the headlights come on, the dash lgiths up and it's doing the same thing it was before.



I'm at a total loss. Hopefully someone here has dealt with this and can give me some ideas? Otherwise I'm at the mercy of the Stealership which for an electrical issue I'm afraid of what that is going to cost me....


Oh, by the way this is a 2006, MCS hardtop.


Thanks to anyone who offers suggestions in advance!!!


Brad

 

Okay, so we need to find WHY the fuses blew.... I assume BCM? Have you checked for moisture? As well as the ECU and make sure all connections are tight and dry? Maybe something in the fuse box is loose... Did you do any eletrical wiring yourself or is all of that stock??

 

I forgot to mention, none of these crazy electrical issues were present before I unhooked the positive terminal on the battery. Before I had the various ABS lights, but none of the electrical issues.

I have not checked BCM, or ECU. I actually don't know what/where those things are.

No electrical stuff done myself, 100% stock MCS except for rims and non-run flat tires but that was like 3 years ago...

 

I did some searching on NAM and found a few things regarding the Body Control Module (BCM) and the Electronic Control Unit (ECU). It sounds like BCMs go bad and cause this exact kind of crazy behavior. I called the Stealership and they want $279.00 for two hours (minimum) diagnostic time to tell me what's wrong.

Looking up the part number it seems like a new BCM is going to be around $450.00 then it has to be 'coded' by the Stealership.

I'm looking for advice here from you guys... Are there things I can do to check my BCM without paying close to $300.00 to Stealership? It seems it's down on passenger side by bonnet release latch so it should be fairly easy to get to. What do you guys recommend?