I have an 86 and the anti lock light came on the dash. Is ther codes that can be pulled that will help narrow the problem. Anyone have this happen to them. Is there a fuse for this/. I dont here the pump come on when i back up now.

 

OK,

This forum has several excellent posts on ABS troubleshooting. Try the archives for "ABS" and let er rip. Should get several hits.

A second general comment is the need for a service manual with regards to your system. Pre 90 cars did not store codes. Bummer. The service manual is very very helpful for this system.

A few things suggested based on your symptoms. Understand with key on, engine off, the light does not go out. Then, when you start the car, no pump checks, etc. Is that correct? Light is on all the time?

With key on, engine off, the ABS brake module will get power, wake up, and should turn out the bulb. When you start the car, the ABS power was interupted, (key in start position, not run), the light again illuminates, ABS module again turns it out, and waits for motion and the pump check, solenoids, etc. IF the light NEVER extinguishes, it suggests the ABS module never received power or ABS module went south. There is a relay, ah, something like ABS module power relay, overvoltage protection relay, whatever you want to call it, that provides power to the ABS module. There are also fuses, fuseable links, and this module relay that can prevent ABS module activity. This is where the service manual shines. The wiring diagrams will direct you to where to check voltage. If you plan on keeping the car, buy a manual.

Check all fuses. See if any other electrical items don't work. Let us know.

dlmeyers 90 coupe zf6 3 speed shocks

 

I agree, get a set of manuals.

One cheap and easy thing to do is check the brake fluid level. Low fluid will set off the ABS light. Although if the ABS pump is not cycling, fluid may not be the only problem.

 

jtfrog,

As suggested, search the archives for ABS. I have replied in-depth to this question several times because I have had a LOT of experience diagnosing ABS problems on my 88. The 88-90 ABS systems don't have codes that can be pulled unless you have a special GM authorized Kent-Moore ABS test unit.

I see that like myself you are from Sacramento, CA. If you want to talk about 86-88 ABS systems in depth feel free to give me a call at 331-6554. I have the GM ABS test unit for the 86-90 systems as well as the pinout box for testing the sensors individually when disconnected from the ABS controller. I'll be glad to run the diagnostics for you for a 12 pack of Guiness.

-Mike

 

Thanks for the help. Ichecked the fluid level and that was ok, I also checked the fuse and that was ok. Tha ABS light did not come on today, but i still didnt here or feel the pump like i normally do. Thanks for your offer Mike. If i cant solve the problem I will sure call on your help. Beer would not be a problem.
Thanks

 

The relays in the C4s (at least in my '87) have a little circuit diagram on them with pin numbers. One symbol shows where the power goes, the other what you need to send a signal to to get the relay to click. In the rear behind the driver seat under the speaker (convertible) is the ABS unit. There are a few relays here. I removed them one at a time and tested them with alligator clips on the battery until I found the one which didn't click when it was supposed to. :yesnod: I replaced that with a new relay and the ABS light went away. :thumbs:

I forgot to mention that on my '87 the ABS would not go through it's cycle - just as you describe. The cycle is supposed to happen when you hit 4mph, whether you're in forward or reverse. ;) Once I replaced the relay all was back to normal in terms of the self test at 4mph. :)


[Modified by Juliet, 12:50 AM 12/4/2002]