[img:36b7dbf37b]http://www.m41a.com/gmc.jpg[/img:36b7dbf37b]

'92 GMC Jimmy SLE
4.3 Vortec
4x4
83K miles

The 'get up & go' is not the problem. Stopping is.
Brake pedal extremely squishy, ABS & brake light remains on. Midas bled the lines (as requested), inspected everything they could and referred me to the dealership. Any advice before what I believe may be an inevitable grand for a new ABS control module...?

Forgot to mention, there is a $60.00 core charge for the old ABS control module... Let's not let this technology get out to the Soviets... remember, they use a #2 pencil...
Tom
[img]http://www.m41a.com/z_temporary/octsig.jpg[/img]

See what happens when you buy an import?

Doh! Never mind.

Russ

pump the brake pedal a few times, then hold it down and start the engine. it should go hard for a few seconds, then slowely start to go down. anything other than that, or any air noises, then the servo could have gone.
Pvt Rich Dowling
A35/TQ2.3.47306E4
UKCM

First, pull the ABS code and tell me what the number is.
To do so, you need to take a paperclip or short section of wire and ground the A and H terminals on the ALDL connector under the dash on the driver's side. Do this while the ignition is in the 'run' position, but do not start it.
H is the second pin from the left, bottom row
A is the last terminal on the right, top row.

The ABS light should dim, and flash the code. A quick example-
Code 21 and Code 32 will be shown as such
*flash, flash* short pause *flash* longer pause *flash, flash flash* short pause *flash, flash*

Let me know what the numbers are. Did this happen spontaneously, or after an emergency stop?
Exo2

I was just about to say that.

Kevin

[img]http://groups.msn.com/_Secure/0TgDnAloXyJBkYBZV7s*Kj9!1Bc8b0FJ!WEmX8BpHJk8yRyABH697OsLy1Bm1knQrHcDDdHqDnRAmyoDB6vy6w!ASmCM57J8W6cyCxY8Y84TWwwCw7UVNAA/Burton%20004.JPG[/img]

"I know I'm human. And if you were all these things, then you'd just attack me right now, so some of you are still human. This thing doesn't want to show itself, it wants to hide inside an imitation. If it takes us over, then it has no more enemies, nobody left to kill it. And then it's won."

He's a monster when it comes to these trucks. Isn't he, fellas?
Understood. But, what do I ground these to? ...or am I just jumping them?

Will do. Thanks SOOO MUCH!! As for how it happened, is a mystery. I sort of bought this one on a gamble. *gulp*
Tom
[img]http://www.m41a.com/z_temporary/octsig.jpg[/img]

Oops, sorry for the misunderstanding. The A terminal is common ground, so just jump the H terminal to it.
Exo2

Got it. Thanks. The paperclip worked like it was made for this.

I'm getting three definite sets of signals repeated 3x each in this order:

35
81
12
Tom
[img]http://www.m41a.com/z_temporary/octsig.jpg[/img]

Alright, now we're getting somewhere

Code 35- left rear speed sensor or circuit open

This indicates either a loose connection to the sensor, or a faulty sensor

Code 81- Brake switch circuit shorted or open

Problem with the brake light switch, which is mounted on the underside of the dash. You'll see two white boxes with plungers attached to your brake pedal lever. One is for the cruise control cutoff, the other is for the brake light switch.

Code 12 isn't an ABS code that I know of. It's 4-wheel antilock (4WAL) system, right? In terms of the 'Service Engine Soon' light, 12 simply indicates 'Diagnostic mode'.

Okay...so it's a 92 4WD.... unfortunately it looks like you will be hunting down some electrical gremlins, but don't give up just yet.

Next step, are any of the fuses blown? If no fuses are blown, it's not a short, but it's a bad connection. We'll take this a step at a time, and with some luck we can get this sorted out. Do you have a multimeter or a continuity tester?
Exo2

It's like watching McGuyver at work!
"How lucky are the few who know where they belong."

This is a HUGE relief to me. Thank you!!
Sorry, Exo. I bailed at this point. It's at the GM service department now. I've opted to keep that appointment since my luck with electrical problems have usually been bad.

Something very cool though... their $79.95 computer diagnostic service offered the same information that you found. It's not going to hurt in this particular case because that amount will roll over to labor. The price they quoted me to fix this is okay and it is VERY sweet to have a one up on their diagnostics equipment. eh?

If the weather was a bit nicer, I would take a stab at this myself. Thank you so much for your feedback on this. I owe you one!

It's ALL Exo2, bud.
Tom
[img]http://www.m41a.com/z_temporary/octsig.jpg[/img]

No sweat, Tom. Let me know how it pans out, I wonder how close to the mark I was. Currently I'm suspecting the brake switch and the driver's side rear wheel sensor need replacement. These can be tested with a multimeter before replacement. If they test good, then it would have to be the wiring between those items and the Electro-Hydraulic Control Unit.

Let me know if anything else comes up, I'll try to lend some advice.
Exo2

Will do, bud. You are a KNIGHT!!!
Tom
[img]http://www.m41a.com/z_temporary/octsig.jpg[/img]

...its a very pretty truck!
[img]http://www.colonialmarines.net/Banner.jpg[/img]

Thanks!! As of yesterday around 2:00 PM, it's back on the road. She's an oldie but boy howde does she rumble.
Tom
[img]http://www.m41a.com/z_temporary/octsig.jpg[/img]

Glad to hear it, Tom. Disappointing to see that the EHCU was the failed part, but at least you got a good deal on it. Glad to offer what help I could, feel free to ask in the future, hopefully the next issue won't be as rough...and won't be for quite a few miles.
Exo2

Just replaced the fuel pump, buddy. That 60 psi reading is the most rediculous thing I've ever seen. Most TBI systems are rated for 9 to 13 lbs. This is a freakin' beast!!

_________________
Tom