sperkins

Helping a buddy patch his car back together after a date with a tire wall.

The only damage from the hit that seems important is that the LF inner tire rod was badly bent which of course caused the steering wheel to be WAY off center when he drove it back to the paddock and on/off the trailer. The code that corresponds to this is C1286 H C which is:

C1286:
The vehicle has driven for 10 minutes without completing steer angle centering.

The steering sensor bias moves greater than 40 degrees after steer centering was accomplished.
Action Taken When the DTC Sets

* The EBCM disables the VSES for the duration of the ignition cycle.
* The Traction Control and Active Handling indicator turns ON.
* The DIC displays the Service Active Handling message.
* The ABS remains functional.


The problem is that the ABS light is on and the DIC shows SERVICE ABS, TRACTION CONTROL etc.
The car is a late 1997 model so the ABS module is mounted on the rear cradle. The left rear took a slight hit and cracked the fender in a few spots, but it wasn't hard enough to even knock the toe out.
Oh yeah - the LF hub bearing has been replaced with a new unit after the accident.

I do have codes in the DIC that directly correlate to the ABS. (See post #6 for update)
C1221 H - LF Wheel Speed Sensor Input Signal is 0
C1222 H -RF Wheel Speed Sensor Input Signal is 0
C1243 H - BPMV Pump Motor Stalled
C1255 H - EBTCM Internal Malfunction / CEBCM Internal Malfunction
C1281 H -Steering Sensor Uncorrelated Malfunction
C1286 H -Steering Sensor Bias Malfunction

Any thoughts are greatly appreciated. Next track day for him is in 2 weeks!!

sperkins

ttt

gmccreary

He may need to borrow my car

fatbillybob

Maybe I'm missing something. My first thought would be to put everything back together check my sensor wires at the wheels etc. Then I would use a generic OBD2 testor to erase all the codes. Then I would test drive to see if codes came back. If there were codes then I would chase those. Have you done that and are you now left with all these codes?

BERETTA

Can you get a scanner on it to see what the steering wheel position sensor analog voltage is? When you clear the code does it set back immediately when you turn the key on or does it have to be driven?

sperkins

That's exactly what I did today. Only 2 codes came back:
C1243 BPMV Pump Motor Stalled
C1281 Steering Sensor Uncorrelated Malfunction


Going to do as Dennis suggested and check voltage at the SWPS (if my scanner will do that) and report back.
Also going to try and cycle the ABS pump on the lift to see if I can get it freed up.

sperkins

Well my scanner will not test the SWPS directly. I don't think that would cause the ABS malfunction anyway, since I just swapped that sensor on another car and it didn't trigger the ABS light - only threw a code.

I've tried to cycle the pump motor on the lift, but cannot get it to activate. I've cleaned all 4 sensors at the wheels too.

Anyone know the procedure to manually activate the pump motor with a hot wire? As I understand it, the rear mounted units are not serviceable through ABS Fixer etc.

Best info I've found on the topic:
http://forums.corvetteforum.com/1560287365-post6.html

sperkins

Well I thought I found the problem. The BPMV is grounded through splice pack G-101 at the right front frame rail. I went to check it for corrosion, but it wasn't even connected. There wasn't even a nut on it.

Disconnected battery for about 20min too.
Code C1281 is now gone.
Code 1243 still active - pump motor stalled.

BERETTA

If you can jumper the ABS Relay to ground while keeping the other circuits in place, it should run the motor provided it is capable of running.
(When the pump motor relay is grounded by the EBTCM, it closes and provides battery voltage to operate the pump.)
Wish you were closer you would be welcome to use the Tech 2

sperkins

You're a bit over my head with trying to jumper the ABS relay, but I'll try to figure out where to do that. You're just rubbing it in with the Tech 2 comment.
You should bring that thing with you to the track.

I have a few other things to try based on some info I received from Bill Dearborn, but those will have to wait until tomorrow.
I did find something odd though. While performing this test:

1. Turn the ignition switch to the OFF position.
2. Using the J 39200 DMM, measure the resistance between the pump motor ground stud and a good chassis ground.
Is the resistance within the range specified in the value(s) column? 0-2 ohms Go to Step 4 Go to Step 9

I get 0.7 ohms if I put my test lead on the eyelet that's on the stud, but I get over 63 ohms if I put my lead directly on the stud itself. What's up with that?

RX-Ben

some studs/bolts/etc are coated with stuff from the factory or gunk over time and are poor conductors.

varkwso

Good luck on this one! Tech 2 is a great tool....we need one in the local community!

sperkins

Ok after 2 days of pulling my hair out I've checked, removed and cleaned all the ground points from A to B. I've tested all the fuses etc and I'm 100% positive the pump motor is porperly grounded. Before I remove the EBCM to test power at pin #8, I really want to know if the pump is capable of running independent of the system. How can I jumper the relay as stated above. I know I can apply 12v at the #8 pin inside the EBCM, but there's gotta be a way to test the motor without going through all that. My gut feeling is that the EBCM is not telling the pump motor to come on, but I need to make sure the motor is good. If I knew the motor was shorted or fried, that would save me tons of work and I could send it somewhere to have it repaired.

Remember, this is a rear mounted early C5 module.

Anyone??

This procedure would also work, but the rear mounted early motor doesn't have the 3 pin connector on it.

BERETTA

Scott, I am trying to copy and paste a diagram for you but it want let me. Copyrighted I guess.
Another way you might be able to power up the ABS Motor is by grounding circuit 969 a gray wire at the BCM, this will allow the ABS relay to power up the ABS motor. It shows to be C1 B7, the BCM is located behind the carpet on the toe board on the passenger side.

sperkins

Thanks Dennis. I'll check that out later tonight when I get the energy. Went at it for another whole day today with no luck, but I hate to give up because I know the only other option for the owner is the dealer and that'll be super expensive and they'll just take the easy way out and want to start hanging parts. At least I know at this point that either the motor itself is bad, or the EBCM isn't commanding it to work.
The motor being bad would be the worst case scenario since it'll have to go to GM (Tech 2). I'm hoping either the motor is just hung up, or the EBCM can be replaced with a working used piece.

Z06cool

I'm sure the owner appreciates all your hard work...

varkwso

exracer28

I will be at Barber for test day next Friday and I can bring my Tech II. I do not think I still have my 97 manual but I can check. I do not think you have to be a SCCA license holder to run test day. We have two cars to checkout, one in the morning and one after lunch so there will be time to work on the car. I will bring o'scope to look at data bus.

sperkins

Update.

I removed the EBTCM from the BPMV and ran 12v to the #8 pin on the module and was able to get the pump motor to power up (See video below).

Of course the ABS still is inoperative and still throwing code 1243.
However, I also got code 1255 which is: "EBTCM internal Malfunction". (2nd time this code has shown).
There is a small hint of moisture inside the EBTCM in the upper right as seen in the pic below. It's obvious that someone has been in there before as there were pry marks on the outside of the case so that's probably where the moisture stain came from.

So at this point I know the pump motor is good, I have a good ground at the motor itself and the internal resistance checks good (see next post). Therefore, I either have a bad EBTCM or a power supply problem to the unit. I'm thinking a power problem should trigger code 1214 which indicates that the relay inside the EBCM that powers up the BPMV pump and the solenoids in the BPMV has failed (Sol Valve relay Contact or coil CKT Open).

Looking for some advise on how to test for 12v to the EBTCM and/or how to "bench test" the EBTCM.



CLICK FOR VIDEO







Someone please shoot me.

sperkins

Also, per the service manual and recommendation from Bill Dearborn, I checked the resistance between terminal 8 on the BPMV and the pump motor ground stud. The specified range is 0.2 - 10.0 ohms. This one checks out at 3.8 ohms. The next step in the service manual is to replace the EBTCM.

I'd still like to verify that I have proper power to the unit before I send this one off for repair.