VetteDrmr

Did a search, found some (I think) relevant info, but thought I'd drop this in and let y'all give the final verdict.

Car is autocrossed once a month minimum (with the attendant ABS engagements) and maintained well.

About 3 weeks ago at my last autocross I started getting the Service (ABS, TCS, AH) warnings on the DIC. Shut down, restarted twice and everything became happy again.

On course (running Toyo RA-1s) the ABS tripped off again without my knowledge and I locked up the fronts, flat spotting and ultimately killing a mostly dead set of tires in the process.

Reset everything after that run, and had no ABS problems the rest of the day (although running on flat spotted tires was interesting!).

Back at home, everything was happy. Then, while passing a couple of slow cars on a back road, I had to abort the pass when an oncoming car came into view. I stabbed the brakes hard enough to engage the ABS, and the C1243 code came back.

Since then frequently I've had to clear the code twice on the first start of the day (or maybe the end of the work day when the car's been sitting for several hours). After two cycles everything seems to be happy.

This morning it was raining, had to clear the code twice, and decided to try an ABS test. Sure enough, the code came back. Then I tried spinning the rear tires to see if TCS would bring back the code; it did. It may be that even though you're running in a straight line the TCS system will apply the brakes after reducing engine power, that would make sense to me but I've got no facts to back that up.

So, is it time to replace the EBCM?

TIA, and have a good one,
Mike

MYLS6

Hmmm sounds interesting but my vote would be to send it off to absfixer.com spend the $200 or so to get it fixed and see if that fixes the problem. I did that with mine when I had the same issues as your having. I dont auto cross or anything but my problem started off as only tossing codes every now (over a 2 week period) and then and I would clear same as you but one day they came and never left. I sent off it came back I re-installed it and I was good to go...there might be another avenue for you to approach that Im not knowledgeable with taking into consideration the auto crossing events ... not sure if I helped but thats my .02cents

87SAM

Sounds to me to be an issue related to the BPMV. Could be a problem with pump ground, circuit wiring or the pump itself. I recently went through this myself. Have you started any troubleshooting? BTW, absfixer does not mess with pre 2001 EBCM’s.

MYLS6

Awe thats good info! SO I guess I was no help!

VetteDrmr

I've sent an email to them anyway. I'll let you know what they say.

Have a good one,
Mike

VetteDrmr

No contact from ABS Fixer, so I guess I'm on my own. I'm guessing there's no one that can repair the BPMV (Brake Proportional Modulator Valve?).

Has anyone every replaced the BPMV? Or, is there some electrical troubleshooting I should work first?

Thanks again, and have a good one,
Mike

jpl99vert

Mike, I have the same problem. I purchased one on ebay(ABS) from Thepartsladi. cost 325.00 They had 9 more left for 98-00.Tryed ordering from Gene Culley, but he cannot supply at this time. Good luck with your problem. Jerry

87SAM

I still think the problem is more than likely an issue with the BPCM. I replaced mine a coupe weeks ago. You need to inspect the wiring leading up to the EBCM for any damage, especially where it passes in front of the radiator and fans. As stated below in the cut and paste from the service, check the resistance from the motor ground stud to a good frame ground point. Remove the EBCM and check the resistance from pin 8 of the BPMV to ground.

At this point is where the manual goes sour as it says replace the BPMV and if that does not work, replace the EBCM.

While the EBCM is removed, use a 12V source with an amp meter in series and apply 12V to pin 8 to spin up the motor. I am not sure what a proper running motor should draw in amps but others have said that theirs have started out around 10 amps or more but after cycling the motor, the current has dropped to the 4 -5 amp range (this could be just a temporary fix as the motor may start to draw more current again after a short time). In my case the current would spike up to 20 amps and keep climbing until I removed the power. The motor was also vey noisy.

After seeing the high current and noisy motor, I was confident that it was indeed a faulty BPMV. I Replaced the BPMV and all is now well. There is a thread out there with a very good pictorial of the 12V source and amp meter in line.

Found the thread I was thinking of by sjbrothers.
http://forums.corvetteforum.com/c5-t...surements.html

From the manual:
DTC C1243 BPMV Pump Motor Stall
Circuit Description
When the pump motor relay is grounded by the EBCM, it closes and provides battery voltage to operate the pump.

Conditions for Setting the DTC
DTC C1243 can be set when the pump motor relay has been commanded off after the pump motor has been on. A malfunction has occurred if the pump motor was on, and the EBCM sensed a stuck or slowly turning pump motor.

Action Taken When the DTC Sets
ABS/TCS/Active Handling (if equipped with RPO JL4) are disabled.
• Indicators that turn on:
o ABS indicator
o Car Icon (TCS indicator)
• Messages displayed on the DIC:
o Service ABS
o Service Traction System
o Service Active HNDLG (if equipped with Active Handling RPO JL4)

Conditions for Clearing the DTC
• Condition for DTC is no longer present and scan tool clear DTC function is used.
• Fifty ignition cycles have passed with no DTCs detected.

Diagnostic Aids
• It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
• An intermittent malfunction can be caused by poor connections, broken insulation, or a wire that is broken inside the insulation.
• If an intermittent malfunction exists refer to Testing for Electrical Intermittents in Wiring Systems.

Test Description
The numbers below refer to step numbers on the diagnostic table.
3. Checks for good pump motor ground.
5. Checks for good pump motor ground through the BPMV.

DTC C1243 BPMV Pump Motor Stalled
Step
Action Value(s) Yes No
1 Was the Diagnostic System Check performed? -- Go to Step 2
Go to Diagnostic System Check - ABS

2 Is DTC 1217 also set as a current DTC? -- Go to DTC C1217 Pump Motor Relay Contact Circuit Open
Go to Step 3

3
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

4 1. Disconnect the EBCM connector.
2. Remove the EBCM from the BPMV.
3. Inspect the EBCM to BPMV connector for conditions which could cause intermittents, such as damage, corrosion, poor terminal contact, or presence of brake fluid.
Is connector OK and cavity free of brake fluid? -- Go to Step 5
Go to Step 6

5
1. Install the J 41247 Pinout Box to the BPMV connector.
2. Using the J 39200 DMM, measure the resistance between the J 41247 terminal 8 and the pump motor ground stud.
Is the resistance within the range specified in the Value(s) column? 0.2-10 ohms Go to Step 7
Go to Step 8

6 1. If connector corrosion or damage is evident, replace BPMV and/or EBCM as necessary.
2. If brake fluid is present, replace BPMV and EBCM.
Is the replacement complete? -- Go to Diagnostic System Check - ABS
--
7 Replace the EBCM. Refer to Electronic Brake Control Module (EBCM) Replacement .
Is the replacement complete? -- Go to Diagnostic System Check - ABS
--
8 Replace the BPMV. Refer to Brake Pressure Modulator Valve (BPMV) Replacement .
Is the replacement complete? -- Go to Diagnostic System Check - ABS
--
9 Repair open or high resistance in CKT 1250. Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?

VetteDrmr

While I haven't had the time (right now my Vette is my DD) to dig into the diagnostics, I have noticed that when the motor is energized there is a significant power drain. Also, today for the first time I had to re-cycle the system 4 straight times before it passed its power-up test. Another indicator to me that the BPMV is degrading farther and farther.

Jerry, I really like ThePartsLadi, not only do they have good prices, but they also stand behind their products. Recently I had to return a 14 month old Optispark and they took it back, no problem. Are you sure that $325 price was for the whole assembly, or just the EBCM?

Thanks again, and have a good one,
Mike

Bill Dearborn

Mike,
When you get around doing the diagnostic on the BPMV besides verifying a good ground at G101 make sure you check the resistance to ground from the motor windings. That is Step 5 in the procedure above. Check from the BPMV power pin to ground (BPMV case) not the EBCM pin to ground.


If the pump motor is stalling because the windings are starting to short to ground it will not be long before the EBCM relay is shot.

Bill

VetteDrmr

Will do, Bill, thanks for the diagram. Hopefully tonight, although ambient temps in the shop are in the high 90s.

Have a good one,
Mike

jpl99vert

Mike, That price was just for the EBCM. Read #7 from 87 Sam. Replace the obvious problem, if thats not it, then go to #8 99% of the time it"s The EBCM. Jerry

VetteDrmr

Well, 87 Sam didn't say which part he was referring to, but I figured it was the EBCM. However, one can dream of getting a $1400 part for $325, can't I?

As far as "replacing the obvious", trust me, I would if it were obvious. Read back through my posts, the system IS operable, BUT only for the first application. I'm going to do the typical checks tonight, but I don't hold out much hope.

Thanks for the reply, and have a good one,
Mike

jpl99vert

Mike, Today I installed my new EBCM. Well that was a waste. Still poped up the old 1243 code. Checked ground resistance from motor to pin G101. All Ok. But this time it pulled a code 1234 Which is the left rear speed sensor. Pulled the wheel and checked connector .replaced, and my codes cleared. Also I am with you on the battery situation. I have noticed that when the car sets for a few days, the battery seems a little sluggish. Could be low voltage to operate the pump. Battery is only one year old. but it has been mentioned before, the Die Hards die early
Keep plugging along, Its good feeling when you find the problem, and fix it Jerry

VetteDrmr

Here's the results of tonight's debugging:

1. BPCV ground stud to chassis ground (not G101): 0.6 ohms
2. After wrestling with getting the unit free enough to pull the two halves apart, all bolts came free easily except the lower right. It was very tight coming out, and after I removed it about 1/3 of the threads looked like there was some kind of loctite on it.
3. Opening up the EBCM the circuit card looked like there was some sort of coating on about half of the card. There also looked like some brake fluid in the corners below the CCA, but when I tried to swab some out with a Q-tip it was dry, almost like a soft silicone.
4. Now the fun part.


From reading through the links and drawings y'all have provided I think the correct lug for the drive motor power is the large lug on the left side of the right-hand connector (i.e. NOT the one the spade is plugged into). The resistance at this connector reads 0.4 ohms at the BPCV ground lug, right on the bottom limit. I connected a 12 amp battery charger up and cycled the motor at least 10 times, running probably 3-5 seconds each time with a small amount of time to keep the jumper wire cool.

Each time the motor would pull the maximum 12 amps the charger would put out, and the motor rpm would start at some speed then start lugging down. I never left the jumper connected long enough to see if the motor would stall completely or not.

This operating characteristic was consistent for each test (i.e. it wasn't "sticky").

I think this is telling me that the drive motor has had an internal failure that is pulling more current than it should and generating less torque than it should (i.e. some windings are shorted).

Am I right, or do y'all have any other suggestions to spare me the $$$$?

Thanks again for all the help, and have a good one,
Mike

87SAM

Sorry about that, I misspelled what I was referring to (sort of cloned the two parts). It was the BPMV that I replaced.

That does seem like a high current, as others have said that they got theirs down to the 4amp range after the motor massage.

My symptoms started about the same as yours. Started out getting the code very intermittently after start up and increasing in frequency as time went on. In the beginning I could clear the code after start up but the time came when it would never clear.

Yes, the price seems to be in the $1300 to $1400 range although I never spoke with Gene personally to see what the exact price would be.

I procrastinated long enough that I got a nice deal on a new BPMV on the forums for sale section.

VetteDrmr

87Sam,

I pulled the Ebay trigger on a complete assembly from a '99 that's being parted out for $320. It's a gamble, but fingers are crossed!

Thanks again, and have a good one,
Mike

87SAM

I thought about replacing mine myself but I still would have to take to someone with a Tech II to bleed the pump. Ended up taking it to a Vette guy and he replaced for $127. Seems like the dealer wanted $230.

VetteDrmr

Yeah, the T2 issue is the only real fly in the ointment. I'm going to probably go down to our Chevy dealer and see how much they'll charge to bleed the system. C4C5Specialist says it's about a half-hour task.

I'll let y'all know what happens when I get this new used unit installed.

Have a good one,
Mike

jpl99vert

Mike, The motor uses a different ground, which goes to pin 101
87 sam, how did you get below the brake lines to get the two insulator nuts off? I cannot even get my hand in that area