Hi all,

Have a Y2K with a few bugs in the system. I have the dreaded 1255 but I am NOT going to take broken as an answer just yet.

Popped this bad boy out to realize it is one that nobody fixes! Now, as I posted in a now-locked (why?) thread, I am going to try rebuilding this sealed unit. If the motor was measured moving slowly (1243 code) I am going to try the jumper wire and spin that bad boy. If the relays are what burned up, its worth a try.

I have been all over the web and in town trying to find the relays (normally closed and open when energized) Bosch Part number
0 332 019 152

Does anybody have a lead on these? I really do think I am on to something here...

Cassidy

 

C1255 indicates there is a problem with the electronics inside the EBCM. It is totally separate from any BPMV issues or issues with the relay inside the EBCM. Replacing the relay inside the EBCM will not fix the electronics problem. Before tossing the EBCM make sure the voltage and ground connections are good and that a proper voltage is getting to it. Checking the system voltage relay circuit will not do this as that is a separate circuit for powering the BPMV. You need to check the power to the electronics and the ground at G108 over by the battery.

Bill

 

Thanks for the heads-up, Bill. I am getting it apart one bit at a time and want to look at what custom SMT IC's are on the board. I am guessing it's an off the shelf processor (why would GM redesign a computer for this, just use the data lines it needs off a stock chip) and I want to see what is going on there. I find it so hard to accept these just "die". Something as simple as "tin whiskers" could form and cause failure. Again, the whole shebang ain't dead; just a part. May be over some folks heads to fix (maybe over mine too) but I'll throw my hat in the ring!

I have the relays that are there open now and will check the leg directions and see if there is a repair/replacement part more readily available than what I have seen so far. It has a funky circuit that Bosch doesn't seem to use often. Should not be this hard, after all it is GM!

Cassidy

 

Cassidy,
This is a bizarre coincidence! I have the same problem right now on my '99 C5. It began throwing the code Friday at the GM dealer while having something else done.

The dealer is telling me they can't find a replacement for the unit. I just received photo's of the circuit inside the module and not only is it clean but there are no IC's visible(There may be another card behind it!). There are just two relays and a dozen capacitors soldered to a very simple looking circuit board. Seems very fixable if it even comes to that.

They invited me to have a look at the car and chat with the tech working on it. I plan to bring my multimeter and check power and ground as Bill suggested. I've never checked to see if the car has corroded ground connectors. Heck, I've never had any problems till now. A bad ground is my #1 suspect at this point.....

I'll keep you updated and please do the same for me!

Mike

 

Make sure you search here and find a way to exercise that ABS motor. I think if you check the grounds AND do that, you may be in luck.

If anybody has a completely dead one of these modules, I would LOVE one that I could hack apart. I am going to cut one open on the bandsaw and see how best to disassemble.

The actual processor and program code are all surface mount tecnology (SMT) and are on the backside of the board. The 6 power in/out pins pass through the board and so do the connectors at the bottom (14 pin). All the others are on the backside (out of sight). I am having a hard time disassembling them, as I think the black connectors at the bottom are fixed to the case (therefore the eyes would like to see one cut open on a saw!). I think desoldering the 14 at the bottom would do it (already got the 6 top ones undone) but there is a good sized mfd cap in the way. Once I am 100% sure I can get it apart, I will just pop that off as they are cheapo to change (would like to read value on it before though).

Good luck fixing yours, I am working on a permanent fix here too, one that others can benefit from. These cars are too nice to have something like this cripple them from state inspections!

Cassidy

 

I've learned quite a bit more about this issue in the last 24 hours. My '99 C5 has an internal problem (code C1255) with the Brake Traction Control Module (BTCM). All the ground connectors on the car are fine.

I've talked to two different shops that refurbish the '01 - '04 units and they have both told me it's too hard to do on the '98 - '00 version. One cited the SMT you mentioned and another said the problem was the epoxy used to hold the card to the case.

Looking at production figures there are potentially 90,000+ cars that could have this problem at some point in their future so I think it's only a matter of time before somebody figures out a solution.

Does anyone know:
1) Who makes (made) the part for GM? Maybe they could be persuaded to reproduce a run.
2) What the circuit diagram is? What the processor number is? ROM source code if any?
3) Is it possible to convert a later production module back to a '98-'00?

I don't know about your state but here in Texas, I'm told a yellow ABS light will still pass while a red brake light will not. I've yet to confirm that, however. Even if true it still bums me out to think I have to drive my car without ABS for an extended period.

EDIT: The yellow ABS light will pass here in Texas.

 

subscribed.

 

Well a funny thing happened on the way home from the dealer. After internalizing the fact my creampuff C5 will have a lit up dash for the foreseeable future, I looked down and the lights had gone out! Hugh?!

I don't know if the code will come back but I've been through at least 30 ignition cycles and no current codes. The moral is "Don't Panic". The fact my system is working properly right now rules out problems on the circuit board with the processor etc. That kind of thing is permanent. More likely is a high resistance connection somewhere or possibly high friction in the pump from sitting. I don't drive the car much and have had problems with the window regulators freezing etc.

Crate

 

UPDATE:

I now have a working TCS module! For how long? I am not sure. Basically, I went through the module and made good, logical upgrades. I cleared the codes, reworked all my grounds and exercised the ABS pump before reinstalling but it seems to be working.

I had one TCS code, cleared it and initiated the ABS system from four different speeds. The system operated flawlessly each time! I can't believe it. We shall see how long it works but for now it seems to be working.

I can't believe it's working. I am pretty happy right now. Anybody have a dead one they want me to try fixing?

Cassidy

 

UPDATE:

2 days of flawless ABS operation. Couldn't be happier with the lights out. Went to get my inspection done yesterday confident in that repair, only to have the backup lights not work and it failed! I bought a new neutral switch (A4 car) and will pop it on soon. Easy enough fix, right?

Today I got traction control to engage and it did trip the 1255 code. I cleared it while driving and it did NOT come back. ABS still is working perfectly. I really do think I am on to something here. Strange that one system would work and the other not. That really is an internal program error, in my opinion.

Cassidy

 

UPDATE:

Now at 5 days and about a tank of gas driven with NO codes or problems. ABS still engages correctly and no weird codes.

I may really be on to something here guys. I am still trying to figure out why one section could "work" and not another. Unfortunately I have spent two days tracing a bad terminal in the underhood power distribution block for the backup relay (relay and backup switch worked fine, but not together, that sucked to diagnose!) so I haven't had much time for tinkering.

Anybody got a dead one of these modules lying around? I would LOVE to fix one and have it back on the road!

Cassidy

 

UPDATE:

Extremely wet DC weather morning. I started the car and got a 1243 C code. Cleared it immediately and drove to work (did not come back on, as you would expect). Engaged the ABS close to work and the code came back, but ABS DID function first. I am going to take the module back out and exercise the pump again (first time it had been on in two weeks) and reclean the contacts in the relay. Might be worth looking over the solder joints again too, now that the PCB is no longer mounted to the case ala the GM wizardry I took off...

We shall see. Hey, I am happy that ABS still worked at all. Now if I can get rid of my turn signal codes (I know, when you get both front ones its the hazard switch).

Cassidy

 

Cassidy, maybe you'll come up with something here. I have only had the 1243 code, but it's bugged me for a couple of years.
I keep exercising the motor, but live in fear of relay or module failure due to the increased current load from the sticky motor.
The bad thing about that is that increased use of ABS or TC, to keep the motor loose, may hasten relay failure if the motor is not really loose.

I just posted on another thread that I saw an add on the WEB for repair of the early EBCM's. They wanted $750! I'll try to find it again, but I think it was when I was searching for "corvette ABS repair" or something like that.

Keep us posted; I really want to keep my ABS. I've driven cars with and without ABs in panic situations, and believe me, ABS can mean the difference between crashing at 30 MPH and stopping with no harm.

DG

 

I have a 99 and the abs/traction control lights are on. I have checked all of the grounds, and removed the ebtcm and sent it to a tech to check the relays and circuit board. The module is good. While it was off,
I ran the abs pump several times using a jumper wire direct to the battery. Pump works fine. No matter what I do, I can not clear the
C1255 code. Any suggestions?

 

Thought this might help you out. As you can see from the subcodes some C1255 faults are due to a ground or voltage disruption. Use the wiring schematic and make sure all input voltages are good and check and clean every ground. I cut off the C5 ground plugs and soldered on ground lugs for each one. I also noticed on alot of the grounds the crimp is around the actual insulation of the wire and some of the pins in the ground plugs are not zero resistance to ground. I also removed the EBTCM plug and cleaned an resprung all pins to insure good connections. Also made a new ground point for the EBTCM and BPMV so they would not be effected by other sources. Make sure ALL grounds are clean and tight. I have not had a TC/AH fault since......before I was getting them on every daily drive.........

I did all of my repairs due to Bill's advise on many threads......

Along with the C1255, a 2 digit Sub Code will set. The first digit is a Letter, and the 2nd digit is a number. Note that only the Tech 2 will display these sub codes, using the On Board Diagnostics through the Drivers Information Center on Cadillac and Corvette WILL NOT display sub codes.

Here is a list of the Sub Codes that may set:

E0, E1, E2, E3, E4, E5, E6, E7 M0, M1, M2, M3, M4, M5, M6, M7

Probable Cause: Each sub code represents a specific malfunction. Most sub codes set due to a malfunction internal to the EBTCM, and can be repaired by replacing the EBTCM. However, EBTCM replacement is NOT always necessary when DTC C1255 is set. Here is a list of exceptions where a fault external to the EBTCM will set C1255.

C1255 E2: This Sub Code may set due to a loss of battery or ground to the EBTCM.

Battery Cable disconnect
EBTCM Fuse Pull
EBTCM harness disconnect
Weak or Discharged battery
Any other interruption of battery or ground to the EBTCM
C1255 E2: Can also set when an EBTCM is first installed on a vehicle. C1255 E2 will be stored as a history code only, and WILL NOT turn on the ABS light. A typical service scenario is when an EBTCM is replaced for a DTC other than C1255. The vehicle again returns with the ABS light on, and C1255 E2 is set as a history DTC along with the original DTC which brought the vehicle in for service. The servicing technician is erroneously convinced that the new EBTCM is defective.

Replace the EBTCM for C1255 E2 only when a source of a battery disconnect cannot be identified and was not set due to EBTCM replacement.

C1255 M5: This Sub Code indicates that the EBTCM has detected a malfunction in the one of the Wheel Speed Sensor Circuits, and sets along with Wheel Speed Sensor DTCs (C1221 thru C1235). Disregard C1255 M5 and perform diagnostics for the other wheel speed DTCs. Only replace the EBTCM if all other wheel speed sensor diagnostics have been exhausted and the source of the DTCs cannot be identified.

C1255 E4 and E6 set together: This sub code combination sets when the pump motor ground circuit has detected B+. This condition can occur if the BPMV ground circuit is shared with other components and the ground bolt is loose or disconnected. These other components are seeking ground, then back-feed into the EBTCM thru the BPMV.

Sorry so long but thought it might help out some 2K owners.....

 

A tip of the hat to Cassidy and Mike, maybe others, who are knowledgeable enough and courageous enough to tear into this problem, learning things that may benefit a lot of people down the road.

 

UPDATE:

After almost two months we are still in business. I have a working system that VERY rarely throws a code. I really do think it comes down to the design of the unit.

What I did to fix mine was open the relays and clean all the contacts with high count (fine) sandpaper, like 800 grit. Then I reflowed ALL solder contacts on the major board component pass throughs (the big connector pins). I removed the screws that held the circuit board to the casing, as everything has different expansion rates (different materials) and that is a fairly volatile environment behind the radiator so that no further cold solder joints would form from expansion and contraction. Ran the pump a good bit while it was apart and I appear to be in good shape.

If the TCS system kicks on, I 'sometimes', maybe one in 10 times, get a pump code. Clear it on the DIC and I am good to go. Then I usually stomp on the brakes, kick the ABS on and make sure it all still works. Never a code after that.

Opening those relays without damaging them is a trick. I would love to have somebody's dead module to document a fix and post here. Is this the be-all, end-all? No. Did I fix a busted vette? Yes. Somewhere on the spectrum that HAS to count for something!

Happy Holidays to you guys. Been a weird year for me and my vette family on the track has kept me sane. I truly don't know where I'd be without my club or friends in the car community.


Cassidy

 

Somebody get Cassidy a module out of a wrecked car or something. You may benefit from his experience down the road

 

Cassidy: Did you ever find a source for the Bosch relay 0 332 019 155? I sent an email to Bosch today trying to source an equivalent replacement. I've spent $800 trying to fix my 2000 EBCM with active handling, and have had no luck.
---Shawn

 

have the same problem.