1990 No ABS: any obvious stuff?

[Aurora40]

So it's becoming more apparent to me that my ABS doesn't work. The "service ABS" light comes on at startup but goes out, but I never hear the thing cycle on in the self-test.

Yesterday, I was doing some 60-80mph stops to see if I could help the brakes out. I think the stock pads are glazed, and probably are original. The rotors look ok, though they have grey and blue banding that hopefully a good pad bedding will remove. Anyway, on one of the 80+mph stops, a front wheel definitely locked up and no ABS ever kicked in.

Are there any obvious/common issues that would cause this before I dig into more complicated ones?

Thanks!

[ZR1 MK]

Checking for codes is the first item to check.

[Aurora40]

Is there a paper-clip-like way to check for ABS codes? Aren't those stored differently than SES-type codes? I would like to eventually pick up a Tech-I, but it's not the first thing I want to buy for the car...

Wouldn't an ABS code cause the light to stay on, though? The bulb is ok because it comes on and off when you first turn the car on.

Thanks! :)

[ZR1 MK]

I think all codes are retrievable as you describe, but Im not familiar with them as I use my Tech 1 or ABS code reader.
Theoretically the light should stay on when codes are present, but I have had codes stored with the light off.

[Jim Jones]

Aurora40, Jeffvette will know how to use a paperclip to get the codes. I believe you jump the A and B, but I don't know which ones they are.

Jim

[Aurora40]

Just a quick update. You jumper "H" and "A" to retrieve ABS codes. All I get is the "ok" code 12. I pulled out the stuff covering the system behind the driver, and everything looks connected and such. I'm wondering if maybe it does the self-test and I just can't hear it over all the other noise?? I think it might help to pick up a Tech-I to go any further, though, as it can let you do/set a lot of stuff to troubleshoot the ABS system.

[Bill]

The only time I felt the test was when I had a problem. But then my abs light came on after about a block. My problem was a dirt build up on the left rear wheel speed sensor. After I brushed off the dirt, I never felt the test again and the light stayed off! Good luck

[zr1mom]

The service books says for doing a functional check that all you have to do is turn the ignition sw on and see if the ABS light goes out after 2 seconds.

For a road test drive for at least 2 minutes reaching at least 15 mph and see if the ABS light comes on. If not you're ok.

A system self test happens each ignition cycle when you car reaches 4 mph in either forward or reverse. The selftest cycles each valve solenoid and the pump motor. If error is detected it will set a Diagnostic Trouble Code.

The Self Test may be heard and felt while it is taking place.

I know with my '90 when backing up I could hear the pump behind my drivers seat.

[Aurora40]

The service books says for doing a functional check that all you have to do is turn the ignition sw on and see if the ABS light goes out after 2 seconds.

For a road test drive for at least 2 minutes reaching at least 15 mph and see if the ABS light comes on. If not you're ok.

A system self test happens each ignition cycle when you car reaches 4 mph in either forward or reverse. The selftest cycles each valve solenoid and the pump motor. If error is detected it will set a Diagnostic Trouble Code.

The Self Test may be heard and felt while it is taking place.

I know with my '90 when backing up I could hear the pump behind my drivers seat.

Yup, the manual only really is useful for diagnosing a trouble code. But imagine if you will, you turn the key on, the ABS light checks out so you know it isn't burned out. Then you start the car up, back out of the driveway and hear nothing. No self test. You drive around, the light never comes on. You slam on the brakes at 80mph and lock up the wheels, no pulsing of the pedal is felt and no cycling of the ABS sytem is heard. Still no light. Yet it seems the ABS system doesn't work at all... What then?

What I think I will do is try to find a Tech-I on eBay. And I really would like to get some more definitive skidmarks to see if they are really locking. I guess I should wait until it rains a bit to avoid flat-spotting the tires in my attempt... And it's hard to find a place where you can get enough speed to lock the wheels. The tires have a lot of grip...

[Jeffvette]

You should feel the ABS fighting the pedal. Romp on the pedal from a 60 mph roll. Push it to the floor like you are trying to force it through the fiberglass.

More than likely the ABS is functioning.

[Nick]

More than likely the ABS is functioning.

Jeff, I agree. I think you gotta hit the brakes awfully hard on these cars in order to engage the ABS.