DTC flash codes - ABS...

Steves95Sierra · December 17, 2004

Help!

Jumping pins A & H on a 12-pin ALDL, I get the following OBD1 flash codes (abs light)...

6 flashes - 8 flashes (x3) = 68

1 flash - 3 flashes (x3) = 13 - which may be normal for 2wd

3 flashes - 6 flashes (x3) = 36

3 flashes - 7 flashes (x3) = 37

Then repeats...

BTW - The Truck is a '95 C1500 SLT

ABS is Kelsey-Hayes 4WAL

Can anyone out there help me figure out what my truck is trying to tell me?

Thanks...

Steves95Sierra · December 20, 2004

Update...

Did find this:

6 flashes - 8 flashes... (68) = A locked motor or open circuit

1 flash - 3 flashes... (13) = System Normal for 2WD

3 flashes - 6 flashes... (36) = Missing left rear VSS signal

3 flashes - 7 flashes... (37) = Erratic left rear VSS signal

Conflicting... So.., does this mean I have a bad relay, motor or pump in the EHCU AND a failing or failed wheel sensor???

This is one of those situations that the more I find out, the more I'm confused?

BTW - In case anyone else is looking, here's some great info on ABS...

http://www.raybestos.com/OnLineTraining/

GM-Tech... you still out there??? Any Ideas???

Thanks - It's 9degs, ice and no ABS...

GM-Tech · December 20, 2004

I don't know about the "left" wheel speed codes you're getting because that truck uses the vehicle speed signal for the rear wheels as far as I know. In other words, there is no individual wheel speed sensors in the rear. It uses the same speed signal that the speedo uses. But, the code means the same thing, just think "rear" wheel speed signal rather than "left" rear wheel speed signal.

Does your speedo work ok? No jumping around, especially at low (~5 mph) speeds, etc.?

The 68, I'm sad to say, is almost certainly a failed BPMV. These were known for their less than robust ABS components. We've replaced more of those on the older trucks than any other ABS system combined.

Unfortunately, I can't locate a '95 service manual at work and GM's online service information only goes back to '98, so there's no diagnostic info I can easily send you. I also have access to Mitchell OnDemand, but they seem to go to extreme lengths at preventing one from easily copying any of their data.

Steves95Sierra · December 21, 2004

Oh boy... I was kind'a afraid that would be the case...

Thank you very much for taken the time to research this for me. You've been a tremendous help!

Regarding the speedo.., it appears to be working fine, even at slow speeds.

As for the '68,' do you think I could get away with just having the EHCU rebuilt, or do you think the whole BMPV aught to be replaced?

The truck is 10 years old, but has less than 60K on her and is otherwise in great shape (regularly maintained). The hard part is deciding to dump the $700.00+ into her to replace the entire BMPV.... Merry Christmas to me...

Hmm - does GMC sell Kelsey-Hayes rebuild kits?

Again - Thank you very much for your help GM-Tech. It's greatly appreciated....

GM-Tech · December 21, 2004

I believe there are sites on the Intenet that advertise rebuilt (or they'll rebuild yours) ABS units for these trucks. I don't know too much about 'em since we wouldn't sell anything but a GM part because we have to stand behind it.

Do some research before you spend a lot of money.

Steves95Sierra · December 28, 2004

Update...

Did find this:

6 flashes - 8 flashes... (68) = A locked motor or open circuit

1 flash - 3 flashes... (13) = System Normal for 2WD

3 flashes - 6 flashes... (36) = Missing left rear VSS signal

3 flashes - 7 flashes... (37) = Erratic left rear VSS signal

...

<{POST_SNAPBACK}>

FIXED>>>

(13) = System Normal for 2WD

(36) = Missing left rear VSS signal - cleared on reset

(37) = Erratic left rear VSS signal - cleared on reset

(68) = A locked motor or open circuit - A hung ABS pump motor...

This from Mr. ABS himself (Mr. Gavin Curtis at http://www.circuitsolutions.info)...

"You need to verify that the pump motor is working. Just unplug the ABS pump motor from the control unit and directly power the motor with 12 volts.

If the motor runs, then the ABS control unit may be at fault.

If the motor does not run... you might try gently rapping on the side of it with a plastic mallet or large screwdriver handle. Sometimes one of the motor brushes get stuck in their holder.. and tapping can free them. Don't use a metal hammer as the ceramic magnets in the motor case can be damaged if hit too hard. "

SUCCESS!!!

Thank you Mr. Curtis...

CircuitSolutions.info