Anyone with ABS troubleshooting knowledge?
Thread Starter
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Anyone with ABS troubleshooting knowledge?
No ABS! No warning lights to give a failure indication. No codes, no anti-lock warning light before start-up.
Bled the brakes per the General's book, LR, RR, LF, RF. The ABS self-test is not engaging at the start of a drive, after a shutdown. Checked the Brake and Gauge fuses, A-OK. Checked for power at the relay module, A-OK. Hit it with a hammer, (I felt better
) no change!
I remember hearing the ABS self-test run, a day ago or so ago.
Next step? Any thing I'm overlooking or other areas to check?
-JRC-
Bled the brakes per the General's book, LR, RR, LF, RF. The ABS self-test is not engaging at the start of a drive, after a shutdown. Checked the Brake and Gauge fuses, A-OK. Checked for power at the relay module, A-OK. Hit it with a hammer, (I felt better
) no change! I remember hearing the ABS self-test run, a day ago or so ago.
Next step? Any thing I'm overlooking or other areas to check?
-JRC-
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by TIMSPEED
Did you check the pump, in the drivers side storage compartment? Did you check ALL of the fuses? IIRC, there's a fuse or relay behind the DIC.
I wacked it again, just for good measure. A relay behind the instrument cluster? Those guys at GM sure made it easy to troubleshoot these *&@#^&% pieces of ()*&!I'll be better when baby's working right........
Safety Car
Joined: Apr 2003
Posts: 3,793
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From: VA
Have you used the ABS since the last time you heard it? Don't know the vette for sure but in other cars the only time you hear that is when the pressure has dropped off. Pretty sure I don't hear it every time I start my vette even after sitting for a few days.
Last edited by VenkmanP; Aug 2, 2004 at 01:24 AM.
Thread Starter
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by steve9899
Have you used the ABS since the last time you heard it? Don't know the vette for sure but in other cars the only time you hear that is when the pressure has dropped off. Pretty sure I don't hear it every time I start my vette even after sitting for a few days.
-JRC-
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Team Owner
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From: Summerland B.C. Canada
Originally Posted by JrRifleCoach
The ABS does a "self-test" at the start of each "session" There should an ABS or anti-lock brake failure warning if it is not working. The test is very auditable. Some CF posts have questioned what the noise is not realizing it is GOOD noise! This has been the case for my 86 until recently.
-JRC-
-JRC-Have you tested the brake fuse and gauge fuse ??
Burning Brakes
Joined: Feb 2000
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From: Camden SC
OK, here is my understanding of how this system works.
With key on-engine off, power flows through the power control relay, to the computer, and the computer turns off the "ABS" light on the DIC. Now, if you are not seeing the advisory light with initial key on, that suggests to me the bulb is burned out. It is quite possible to have a bad bulb and another problem. No pump noise means the computer is not commanding a self test. You mentioned you checked the relay. Was it the power control relay? Understand the power output to the module was good? There is a control side to that relay that will also have 12 volts. The critical volatage is on the output side to the brake module. If that is not there, the light will not go out, and there will be no self test.
I would start with checking the bulb. I spent a lot of time with my 90's ABS. The previous owner thoughtfully removed the bulb, the module had a bad circuit, darn light must have bothered him.
Good luck and let us know.
dlmeyers 90 coupe zf6 3 speed shocks
With key on-engine off, power flows through the power control relay, to the computer, and the computer turns off the "ABS" light on the DIC. Now, if you are not seeing the advisory light with initial key on, that suggests to me the bulb is burned out. It is quite possible to have a bad bulb and another problem. No pump noise means the computer is not commanding a self test. You mentioned you checked the relay. Was it the power control relay? Understand the power output to the module was good? There is a control side to that relay that will also have 12 volts. The critical volatage is on the output side to the brake module. If that is not there, the light will not go out, and there will be no self test.
I would start with checking the bulb. I spent a lot of time with my 90's ABS. The previous owner thoughtfully removed the bulb, the module had a bad circuit, darn light must have bothered him.
Good luck and let us know.
dlmeyers 90 coupe zf6 3 speed shocks
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Originally Posted by AGENT 86
I read that you will only hear the secondary test(modulator) when car is first started and reaches 4 mph.
Have you tested the brake fuse and gauge fuse ??
Have you tested the brake fuse and gauge fuse ??
QUOTE dlmeyers, I would start with checking the bulb. I spent a lot of time with my 90's ABS. The previous owner thoughtfully removed the bulb, the module had a bad circuit, darn light must have bothered him.
Many thanks for the tip. I will be pulling the DIC out tonight as well.
My biggest fear is having to take her into the Chevy dealership for troubleshooting. I go "water tight" just thinking about those guys charging me for their "learning curve"
I figure between the resources here in the forum and the service manual I/we should be able to solve this easily. 
-JRC-
Last edited by JrRifleCoach; Aug 2, 2004 at 12:41 PM.
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Last edited by JrRifleCoach; Aug 3, 2004 at 02:11 AM.
Drifting
Joined: May 1999
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From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
JrRifleCoach,
Do a search for ABS threads where I have answered. In the past I've posted extensive tips on troubleshooting the early C4 ABS. Since you live in CA, if you ever get out to Sacto look me up and I'll be glad to run a full ABS test using the GM authorized Kent-Moore ABS test system for the early C4. I bought it off a retired C4 mechanic a few years ago to use on my 88. It tests the ABS controller, relays, pump, modulator.
Do a search for ABS threads where I have answered. In the past I've posted extensive tips on troubleshooting the early C4 ABS. Since you live in CA, if you ever get out to Sacto look me up and I'll be glad to run a full ABS test using the GM authorized Kent-Moore ABS test system for the early C4. I bought it off a retired C4 mechanic a few years ago to use on my 88. It tests the ABS controller, relays, pump, modulator.
