ABS light diagnosis
Thread Starter
Melting Slicks
Joined: May 1999
Posts: 2,037
Likes: 0
From: Sarasota FL
ABS light diagnosis
I'm getting a constant ABS light. I've checked the fuses that the book suggests and they're OK. The next suggested step is to use an ABS tester, which I doubt I'll find. What's my next step - lots of wire tracing and DVM work? Through my archive search, I found a bad link to vettenuts post on pulling ABS codes. Anyone have a good link or info. Thanks.
Melting Slicks
Joined: May 2001
Posts: 3,270
Likes: 26
From: Winchester VA
Cruise-In V Veteran
Re: ABS light diagnosis (Aaron's 87)
You can get a cheapie code scanner at your local parts store. They are a little bigger than a pack of cigs. You plug into the ALDL, put the switch on ABS or ENGINE and start counting blinking lights. They will usually have a book with the code definitions as well. Cheap and easy way to narrow down your diagnosis. Best of luck
Pro
Joined: Nov 2000
Posts: 642
Likes: 0
From: Huntersville NC
Re: ABS light diagnosis (Aaron's 87)
Aaron, You didn't mention wether your car is a coupe or a vert. The reason I ask is because I have a vert and came to find what I think is either a design flaw..or serious owner screw up!.. My ABS light came on several months ago. Using the diags listed in the service manual I finally opened the compartment behind the drivers seat an pulled the inner box out only to find about 3 inches of water in the compartment that houses the ABS distribution unit. Needless to say it had shorted the power wire. My only problem was that the previous owner had an aftermarket alarm installed and all the wires converged up front by the drivers side where the manual says to look for an inline fuse. So I never could find the wire to replace the inline fuse. I sitll need to run a new wire to power up the ABS again and I also nee to drill a hole to drain the water from the compartment should it ever happen again. I know it doesnt solve your problem but maybe look in the rear compartment behind the drivers seat and pull the inner box to get a visual of the ABS unit itself.. :rolleyes:
Race Director
Joined: May 2000
Posts: 17,101
Likes: 4
From: No more yankee my wankee, the Donger is tired!
Re: ABS light diagnosis (Aaron's 87)
Go even cheaper. Use a paper clip. It's the A-H terminal. Come back with the codes you find.
Nevermind, just saw it's a 87.
[Modified by Jeffvette, 10:56 PM 3/18/2002]
Nevermind, just saw it's a 87.
[Modified by Jeffvette, 10:56 PM 3/18/2002]
Burning Brakes
Joined: Feb 2000
Posts: 958
Likes: 1
From: SF Bay area, CA USA
Re: ABS light diagnosis (Aaron's 87)
Does the ABS light come on as soon as you start the engine or only after you start moving forward. If it only happens after the car starts moving forward it may just be a wheel sensor. I had a bad rear wheel sensor. It was damaged when the wheel bearing wore so much that the sensor hit the abs sprocket (what ever you call the gear that the sensor reads) and snapped the tip off the sensor. Start by visually inspecting the wheel sensors.
Pro
Joined: Nov 2000
Posts: 642
Likes: 0
From: Huntersville NC
Re: ABS light diagnosis (devilfish)
Fish,
I'll recheck the manual when I get home tomrrow.. I'll get the color etc..Should be right up front by the battery down the firewall on the drivers side near the outside. Problem was mine has a big relay for the alarm there now. Did you have the same problem as mine ?
I'll recheck the manual when I get home tomrrow.. I'll get the color etc..Should be right up front by the battery down the firewall on the drivers side near the outside. Problem was mine has a big relay for the alarm there now. Did you have the same problem as mine ?
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Re: ABS light diagnosis (Daves90)
thanks.
yeah. Both my ABS active and Service ABS light or on all the time. I cant get anny codes from the abs computer eihter.. I open up my ABS computer and i found ALOT of corrosion in it. SO I tought the ABS computer whas dead.. BUT I didnt have a clue about the fuse you talk about. So myaby thats it:)
yeah. Both my ABS active and Service ABS light or on all the time. I cant get anny codes from the abs computer eihter.. I open up my ABS computer and i found ALOT of corrosion in it. SO I tought the ABS computer whas dead.. BUT I didnt have a clue about the fuse you talk about. So myaby thats it:)
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Thread Starter
Melting Slicks
Joined: May 1999
Posts: 2,037
Likes: 0
From: Sarasota FL
Re: ABS light diagnosis (Aaron's 87)
Coupe. The light comes on as soon as I I start it. It never does it's 4 mph test. A paper clip won't do it, as the ABS system is seperate from the ECM on an 87. I either need a Bosch ABS tester or a lot of time to test wires. There was metion in the archives of a way to test ABS (posted by Vettenuts), but the link was bad and I don't know if it was for C4s with seperate ABS controllers.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: ABS light diagnosis (Aaron's 87)
A good GM dealer will have an ABS tester which diagnoses the ABS. It found a defective wheel sensor on my 87 and after replacement, my ABS has been working ever since.
Drifting
Joined: Mar 2000
Posts: 1,630
Likes: 1
From: Woodstock GA
Re: ABS light diagnosis (Aaron's 87)
It's probably one of the two relays on the top of the brake module there is a silver one and a black one one is a motor relay and the other one is a solenoid relay(which is probable the one that is bad) if either one of these relays are bad the light will stay on all the time, there is also a power relay up by the ECU which could also be bad but my bet is it's the solenoid relay.There are no codes on a 86 to 89 ABS system so you have to go by symptemps it the light comes on while driving look at speed sensors if the light comes on and stays on look at relays or ECU False cycling check weel sensors and grounds, wheels locking up check module and so on.
David Fulcher
David Fulcher
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Re: ABS light diagnosis (David-F)
I have the same probleme, the ABS active AND service ABS light is on as soon as I start the car. I cant get anny codes. Could it be one of the relays ?
Le Mans Master
Joined: Oct 1999
Posts: 9,713
Likes: 3
From: Sachse Texas
Cruise-In I Veteran
Cruise-In II Veteran
Re: ABS light diagnosis (devilfish)
Check all the wheel sensors and see if they have metal dust clinging to them like they are magnetic. If one does not have the dust, it could be out.
Drifting
Joined: Mar 2000
Posts: 1,630
Likes: 1
From: Woodstock GA
Re: ABS light diagnosis (devilfish)
On 90 and 91 you have to use a paper clip and jump terminals A to H that's top right amd bottom left second one in then turn the key on and watch the Service ABS light for the codes and let us know what you find.
David Fulcher
David Fulcher
