Chev G20 Van; Brake light and ABS light on

Greetings.


93 Chev G20, just turned 100,000 miles.


We only put about 3 to 4 K a year on this Van. Use it for vacation trips, pulling my boat ect. Last trip out it started pulling to the right. Initial pull when I first hit the brake, (no matter how hard or lightly I apply braking) and then it straightens out. When sitting at a stand still with the brakes applied, when I first let off of the brakes I can feel the wheel come back left a bit. Seems strange. At first it had no warning lights, just strange behavior. There was a lot of brake dust on the left wheel as opposed to the right, so I figured the left caliper was sticking and was engaging slightly after the right. Anyway on the trip home (500 miles out) I get a brake and ABS warning light. Made it home OK and since then have replaced both calipers, and brake pads. The original caliper was tight & sticking, but I still have a pull to the right. Also the ABS unit seems to not be working. I do not hear it spooling up and doing its check. If I slam the brakes I can lock them up. That has happened once before and after unplugging what I think was the DRAC unit (white module by the parking brake) and the ABS control module (black module by the parking brake) and reconnecting them, it started to work again. No success this time with that approach.
I am thinking it may be a bad ABS unit (with the motor ect) mounted under the Van. I don’t want to just start throwing parts at it. Especially real expensive parts.

Does anybody know how I can retrieve the codes on the ABS, what the codes are & generally how to proceed from here? If anybody has any other ideas; I may be going in the wrong direction and some other problem may be holding the ABS unit out.
Any ideas? Any thoughts?

Thanks! :confused:

On the brake pull also inspect front brake hoses.
Pull antilock fuse and it it still does it it is mechanical part of brake system or front end parts.

4W or just rear W antilock brakes?
On the ABS brake operation and if a 4W anti lock you will need a scanner to test and get codes.
Let us know which system it has.
MT

Thanks MT

It is 4W ABS. It is a 93; I think that was the first year for 4W ABS on G20 Vans. Anyway according to the owners manual and the original window sticker from when it was on the dealer lot, it has 4W ABS.

I pulled the fuse that was labeled brake. According my manual, the fuse labeled brake is for the antilock brakes & the speedometer. That probably explains why the trans wouldn’t shift right with the fuse out. Anyway the Van still pulled right. So I will continue to look for a mechanical or hydraulic problem.

I jacked the front wheels up & the left is still dragging while the right spins freely. You may be on to it about the brake hose. Perhaps if it is breaking down internally & is restricted, it would delay the left when I first apply braking & cause the right to grap first. I’m thinking that when I release the brakes the restriction is preventing bleed off and keeping pressure on the left caliper causing it to drag more than the right. When I replaced the calipers, I initially did a gravity bleed. Now that I am thinking more clearly, it did take the left side quite a while longer to bleed out. Once I had fluid at the bleeder it was not flowing as freely as the right. Seems like it may be restricted. That will be the next thing I’ll check.

Just Curious – Why the ABS unit is not spooling up & doing it’s check? Is it disabled when it senses mechanical or hydraulic problems? Will I have to reset anything after I fix any other problems or will it come back online when all is well mechanically?

The ABS works off of wheel speed sensors and only kicks in when a wheel is locking up or spinning.

The ABS codes clear each time the key is turned off and on.

If it still has a problem the light will come back on each time you turn on key or drive.
Good Luck
MT

Update:

Partial success But ABS is still not functioning.
I replaced the left front brake hose and that took care of the original problem of pulling to the right. The van is braking good and perfectly straight. Both wheels spin freely with no dragging.
I still have The ABS light and the Brake light on. The ABS unit seems to not be working. I do not hear it spooling up and doing its check. Also if I slam the brakes I can lock them up.
Does anybody know how to check the ABS unit, or know what I should check and how to proceed from here.:1zhelp:

Thanks,

Ventura HiWay

Pull abs codes.
Use a abs capable scanner or jumper pins H and a and post back codes.
MT

Thank you MT,

I jumped A & H pins & pulled the codes. The codes flashed 61, 62, & 12.

I do not have access to an ABS capable scanner so I appreciate the info on how to pull the codes.

Ventura HiWay

You just got codes.
Code 61-62 is a reset switch code.

But I would clear and double check codes.

61 or 62 code repair flow chart says replace the BPMV.
Yes the hole thing/the complete ABS unit.

OK
How do I go about clearing the codes?
I will clear them & double check.
Are we talking about the ABS unit mounted under the van with the electric motor and all the electrical connections, brake lines ect. What does BPMV stand for?
I will replace the BPMV if necessary. I will be glad to know what the problem is. I didn’t want to throw parts at it until I knew what was up.

61 -62 reset switch code. Is there a switch that I need to reset?

Thanks for your help and the Info. And thanks for telling me how to pull the codes without a scanner.

Ventura HiWay

Key on jumper h and a pin then remove jumper and jump again untill abs light comes on.

Or try to
Unplug the abs computer or pull fuse or disconnect the neg battery cable should clear codes.

The reset switches are built in the BPMV.
No replacing or setring switches.
Just replace the BPMV.

BPMV is Brake pressure modulator valve.
The big hole thing or ABS unit.

Well whatcha know,
My 93 G20 is doing the same thing Anti lock and brake light both on, however on mine the abs light light came on a long time before the brake light did.
Does anyone have any idea where I might find a fuse diagram for this vehicle??

IF RED BRAKE LIGHT IS ON CHECK THE REGULAR BRAKE STSTEM
Owners manual use has the fuse locations.
But I do not think your problems is a fuse.

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