Hey guys... First time here and I have a lot to tell you concerning this issue.
The multifunction relay module supposedly (from the dealer) controls the Body Control Module (BCM) power functions. It is more commonly known as K134 multifunction relay module (GM# 90 494 163).
Here's the scoop:
A few months ago my 2001 Catera started exhibiting some really strange electrical problems. First the sunroof failed to open and close. Then it started opening and closing, on its own, with the switch always in the closed position.
Next the car's radio started intermittently flaking out. When the radio would lose power the trunk pop, fuel door, and OnStar would also be affected. From research I found the relay can also cause problems with vanity mirror, power locks, and fog lights.
Here's where it gets better:
Two days ago, while my wife was driving the car, the engine just stopped running while she was driving. She called me and I arranged to have the car picked up. When I got to the car it started right up and I drove it home (appox. 25 miles) without a hitch.
When the engine failed I spoke with a local mechanic who posted the issue on iATN.net. The popular vote for the cause of all these symptoms was the K134 module.
After my wife's initial encounter with the failing engine, the car ran great... Until today.
I took the car out this morning for about 20 minutes and the engine just shut down. I had the car towed to my house and when it arrived it started right up again... Huff
I ran the car to my local mechanic for diagnosis... NO BCM or ECM codes set. I called the local Cadillac dealer and inquired about the K134 module and was told they had never heard of anything called a multifunction relay module. The dealer said the likely cause was the $700 BCM and I should bring it right in for service. Well I pulled the K134 module and ran it to the dealer and plopped it down on the desk in front of the parts jockey. He looked up the module's number and said, "Yeah that's the multifunction relay module for the BCM." Oddly enough the same person two hours earlier had never heard of this part. I'm only writing this part as a warning for others... Had I listened to the dealer I would have spent nearly $1000 for the BCM and not had the car fixed.
The module is located (on the 2001) in the upper left hand side of the dashboard, behind the air vent. If you pull the main and lower kick panels the module is fairly easy to remove.
I had read that retacking the solder joints is a possible fix but I'm not willing to take that risk especially when the engine fails. I did inspect the joints and none of them were cold.
When I removed the module the car had been sitting off for nearly 1 hour. Two of the relays in the module were so hot they burned my fingers, telling me these relays were still energized well after the car was turned off.
The mechanic at the Cadillac dealer said the K134 controls multiple power functions within the BCM. As these little problems such as the radio and trunk doors progress, the k134 gets so bad that it confuses the BCM. When the BCM gets too confused it shuts the car down.
I ordered the module this morning and paid $85.77, $90.92 with PA sales tax. The part should be in tomorrow. After it's installed and tested I'll let you know the outcome. All in all this little bugger sure can cause a lot of seemingly unrelated glitches in the Catera.
and I changed it out. So far I have driven it for about an hour total and everything is working great. Volume up, trunk opens, fuel door opens. Once you find the Multifunction Module everything else is easy. Just un-plug old one and plug-in new one. It is gray plastic box with pins on one side to connect wire harness and it is about 2" by 4", located in the upper left hand side under the steering column. Like I said once you find it the rest is easy. The part number is the same as I stated in the original thread. Good luck. Let me know if it fixes everything for you guys.
