(a little clarification - this car sat on the street in some bay area coastal town for three years and didn't move. It's beautiful but salt residue is all over the wheels and brakes, and rusty parts of the back undercarriage look like nine miles of bad road)

Hey folks - ABS and TCS are not working on my 2003 - C1243. If I clear the code while driving and step on the brakes before the error codes comes up again, I can feel ABS engage in the pedal but it is momentary and goes away after which the ABS and Active suspension lights come on again.

The solution I am seeing on youtube is this odd procedure of separating the brake control module (top circle) from the ABS module at the front left of the car and re-soldering 5 particular points on the back of the board. Start the car after that and all the systems work. Anyone else try this and found it to work? I have disassembled and cleaned 4 chassis grounds up front (like the one circled on the left) to no avail. What about this plug (bottom circle) going to the ABS unit? It is covered in what I assume to be power steering fluid since there is a leak there. Does this plug go bad or have a ground that plugs in on the left?

I do have what appears to be a generic Tech 2 scanner, so if anyone with knowledge of that can volunteer ways to look at the system with that, much appreciated. I am a computer geek by trade so I can figure it out, but I am of the opinion that if you're learning to paint, talk to an artist first.

Thank you!

 

I only show C1243 until I am driving a while then I get emissions related codes.

 

I just resoldered mine (today) and my dad's last Thursday. It's not a hard job at all to do - the worst part of it is getting to the board as it is siliconed into the housing. Dad's took me a couple of hours taking my time (his was the lab rat), mine took me about an hour start to finish. Not sure what the plug you have circled is, but I'm sure someone will chime in.

There are 6 T20 screws that attach the EBTCM to the pump, 4 T15 screws on the module cover. you might have to pry a bit between the module and the pump to separate them, Dad's was easy, mine took a bit more effort. Pry from the corners. Be careful not to pry too deep, there is a seal between them that you want to take care not to damage. Once you get it separated and remove the 4 T15's, look for the hole filled with silicone on the board side of the module, clear that out. What I did was thread that hole for a 1/4-20 bolt I had and threaded it in to separate the board from the housing. I used desoldering braid to get rid of the crappy solder GM used and re soldered the connections. When I put the 2 back together, I ran silicone around the housing to re-seal, and around the seal (sparingly!) that is between the module and pump, and remember to seal the hole you used to separate the board from the housing. You don't want any water to get into the module or you will definitely be screwed. I removed the air bridge and went at it from the passenger side.

No codes or lights now!

 

Interesting, well I guess that is what is next then. Only other thing I considered was the right-rear wheel pressure sensor does not work, and read that if the tire pressure monitor cant read a tire it reports to ABS which shuts off. I turned off TPMS with the tech II and nothing changed. So, manual solder procedure it is. Thanks!

 

With the help of an old thread on this forum, I soldered the one in my 2003 C5 3 years ago and it fixed the issue. Good luck.

 

Here is what I am going to follow, seems to be fairly clear.

 

Anyone familiar with the pinout of the EBCM plug? The one indicated in red is black, I wonder if this pin is not in use or corresponds with the burned contacts inside, or is possibly the whole problem. Can I take this plug apart and get that contact pulled out and cleaned?

 

Ha! That's the pin for max fuse 52 which was bubbled, and I replaced.

 

Not so fast, conflicting reports. A 2003 Z06 doesn't use that pin. Mine is not a Z06. Anyone know?

 

Just a guess, but if a base uses that pin and a Z06 doesn't, it could have something to do with the TPMS. Z06 models don't come with them.

I will dig through my FSM after dinner if no one else gets you the right answer.

 

Thank you! I do not think it does use that pin though because after reseating that plug, and finding a ground pin in the aggregate plug on the frame next to it that appeared to be pulled out a little, then after standing on the brakes from 50mph all the lights went out and I could switch active suspension on and off. ABS lights came back on under hard acceleration once, but resetting them fixed it again.

NOW it's easy to see upon inspection, because this car was stored for so long, the right side brakes appear to not be engaging at all as they are still covered in rust and salt. Explains why a hard brake yanks the car to the left. So now the question becomes why are the brakes out on the right side? Maybe that was the side facing the incoming ocean mist. since it was parked on a sidestreet on the coast. I know tire pressure monitor works on the FRONT right, but not the rear.

 

Since C1243 is a stalled ABS pump motor, seems like it makes more sense that the problem would be mechanical rather than electrical given that the car was not moved for three years. I thought the most common code for bad solder joints on the EBCM relay is C1214.

 

Moved to C5 Tech.

 

All the electronic issues are solved. I think.

"Shocks inoperative" and a 36 error codes across the board - changed out ignition switch which powers all the fuse boxes and cleaned the four chassis grounds under the hood. All drain issues went away and shocks came online, leaving ABS and Traction control lights on.

ABS/TRAC lights code C1243 -
1 - unplugged EBCM main plug and cleaned what appeared to be dirt in terminals. Plugged back in.
2 - In the ground plug to the upper right of that unit by he headlight, it has 4 ground wires in it - (I had already derusted and cleaned the connection to chassis) one of them appeared to have a connector lead on the back side that was more visible that the others so I took a probe tip and pushed it in so it was countersunk like the others.
3 - ABS Lights are still on at this point. I took a GM tech ii unit and ran the ABS tests and they would intermittently pass then fail. Before, all they did was fail and complain of "EBCM relay turned off". These are 200 bucks or so and invaluable. I got Lucky, mine came with the car.
4 - Took the car out and put it into diag mode in the TCS category with the C1243 code showing. I got going 50 mph, reset the code and when the ABS lights go out for a moment, I slam on the brakes. ABS Lights come back on when I let off brakes. Three more times, light stayed off. Car stops evenly now with no error codes at all. Shizaam!

Want to know the kicker? I bought this beautiful low mileage car for 2000 bucks because of all these problems that I fixed it with a little detective work, THIS FORUM and a 85 dollar switch. Thanks to all that helped, as well as those whose previous posts were invaluable on how these damn things are put together.

I'll be frank, the previous owner had this gifted to him by his nephew, a car collector, and has a long history with the car including racing it on some track in California when it was only 2 years old. I bought it because he had a massive stroke (he is also my landlord, we live in the same house with me downstairs) 3 weeks ago and I bought it for what I had available to provide money for his care. Now it looks like I can get my investment back several times over, the profit from which will go to widening his doors for a wheelchair, etc. It feels good to provide a gift like that when he was not expected to survive. Merry Christmas!

 

Read the entire post and good for you on fixing the old C5 up and for helping your landlord out. U will never go wrong doing the right thing. Good for U brother, GOD bless. Hope your landlord improves in the new coming yr.