I have a 3800 series II swapped 87 GT with a stange issue and any idea will be much appreciated.
As the post title suggests I get a check engine light when I apply the brakes.. The CEL is like a 4'th brake light since it goes away quickly when releasing the brakes.
The first thing that comes to my mind is a wiring issue at C203 connector.
The CEL light and a lead from one of the brake switches both go to that connector.
The C203 is located under the center console, below where the OEM fire ECU lives.
C203-C is wired to the CEL light C203-P is wired to the brake switch
I don't know if this is your problem, but it might be a place to start.
Dug deeper and all wires/connections at C203 look solid.. I did some checking around the brake pedal switch and it is not the brake switch triggering the SES light but the TCC switch next to it.
Additionally, I'm getting a P0341 code which I thought was a different issue all together but I have no idea anymore.
Does it happen when your parked w/ transmission in neutral/park? Or only when Driving?
If only when Driving... Is likely Wiring problems that angry from iffy motor/trans mounts letting the engine pulling or pinching the wires. Or bad exhaust melting the wires now then soon can cause a fire.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Checked the wiring and it all looks fine I have replaced the ICM since I have a P0341 code and once the new ICM was installed the check engine light when braking went away. Really weird...
I still have the P0341 code after a 15 min drive which is a world of pain. New hitachi coils, New Standard ICM etc.
Still trying to sort out the electrical gremlins...
Sorry to resurrect this but I would like to provide a summary of my pursuit of this gremlin.
The check engine light when pressing the brakes was due to the gearbox being overfilled with oil. My "genius" mechanic dumped a bucket load in there and after I've drain it to the correct level all is well.
The P0341 is most probably caused by the ICM/CPK/CPS harness, seems OK for now after replacing it, let's hope it killed it.
The check engine light when pressing the brakes was due to the gearbox being overfilled with oil. My "genius" mechanic dumped a bucket load in there and after I've drain it to the correct level all is well.
Wow, after all these years here, nothing much is "new"... but that is! Although I don't understand the connection between a CEL and too much oil in the tranny, thanks for reporting back.
[This message has been edited by Patrick (edited 11-08-2024).]
Sorry for the confusion, I got excited finally getting it solved.
I had two issues, main one, which is subject of this thread, was my "4th braking light" which triggered the CEL when pressing the brakes. This was due to too much in the gearbox which created high oil pressure.
Second issue was a P0341 which I thought was somehow connected. It wasn't. It was the ICM harness.
Originally posted by Rightasrain: It happens in all trans gears and when the car is both on or off..
If the check engine light was coming on with the key off and brake pressed, then it is related to the brake switch wiring. The ecm can't activate a DTC and turn on the check engine light with the key off. The brake light circuit is one of the few circuits that has power while the key is off.
quote
Originally posted by Rightasrain: I had two issues, main one, which is subject of this thread, was my "4th braking light" which triggered the CEL when pressing the brakes. This was due to too much in the gearbox which created high oil pressure.
While overfilling an automatic transmission isn't good for it, it won't link the check engine light to the brake pedal.
I suspect you still have a wiring issue with some worn insulation between the brake wires and the check engine light wires. The issue went away because the wires are no longer touching, but the issue hasn't been "fixed".
[This message has been edited by fieroguru (edited 11-09-2024).]
While overfilling an automatic transmission isn't good for it, it won't link the check engine light to the brake pedal.
The OP referred to it as a "gearbox" which leads me to believe it's a manual transmission... but nowhere in this discussion does he actually make it any more clear.
[This message has been edited by Patrick (edited 11-09-2024).]
The OP referred to it as a "gearbox" which leads me to believe it's a manual transmission... but nowhere in this discussion does he actually make it any more clear.
He mentioned TCC, which only exists on automatics. He also referenced pressure, and Fiero manual transmissions do not generate pressure, but automatics do as well.
Dug deeper and all wires/connections at C203 look solid.. I did some checking around the brake pedal switch and it is not the brake switch triggering the SES light but the TCC switch next to it.
quote
Originally posted by fieroguru:
He also referenced pressure, and Fiero manual transmissions do not generate pressure, but automatics do as well.
However, automatic transmissions (as well as manuals) do not generally trigger a CEL ... so it was difficult to make total sense of this thread.
... so it was difficult to make total sense of this thread.
