Intermittent Service ABS Light
Thread Starter
Burning Brakes
Joined: Mar 2009
Posts: 830
Likes: 6
Intermittent Service ABS Light
Team, had the rear brakes down about a month ago. Problem began after that. Before I take it back to mech and complain, I would like to know what it might be. Brakes work fine.
Been working on some hard launches as I have had an odd issue with the feeling of slipping in first & second. Not always, but occassionally and I have Pro Solo comming up so hard launches are worth practicing. So that's the bacground. Sometime now during hard lanches or cornering the Service ABS light will come on and stay on. Not always, just sometimes and if you turn the car off and on it clears. Any ideas?
Been working on some hard launches as I have had an odd issue with the feeling of slipping in first & second. Not always, but occassionally and I have Pro Solo comming up so hard launches are worth practicing. So that's the bacground. Sometime now during hard lanches or cornering the Service ABS light will come on and stay on. Not always, just sometimes and if you turn the car off and on it clears. Any ideas?
Safety Car
Joined: Jun 2006
Posts: 3,629
Likes: 28
From: FL
Since you mention hard launches and braking I will toss this out there. Check the fluid level in the master cylinder, the sensor located there is very sensitive and will cause such issues even if the fluid is just slightly low.
Best of luck, hope it is something that easy and simple.
Best of luck, hope it is something that easy and simple.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
i'd pull the sensors - clean and also check the connections. hopefully it's something simple like that. a bad bearing/hub assembly can sometimes cause the ABS light to come on, and hopefully it's NOT that....
keep us informed - it will just add to our knowledge data base.
keep us informed - it will just add to our knowledge data base.
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
If the master cyl is full, the next easiest place to look would be for something that relates to the recent brake work, since a problem that crops up after a repair is quite often related. Possibly the rear wheel speed sensors or the wiring were disturbed. If that is all ok, look for a code stored by the CCM (not ECM). Don't know the year of your car, but OBD1 cars are self-scanning and the codes can be read through the DIC buttons.
Thread Starter
Burning Brakes
Joined: Mar 2009
Posts: 830
Likes: 6
If the master cyl is full, the next easiest place to look would be for something that relates to the recent brake work, since a problem that crops up after a repair is quite often related. Possibly the rear wheel speed sensors or the wiring were disturbed. If that is all ok, look for a code stored by the CCM (not ECM). Don't know the year of your car, but OBD1 cars are self-scanning and the codes can be read through the DIC buttons.
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
http://www.corvette-guru.com/uploads...CMCodePull.pdf
http://www.corvettebuyers.com/c4vettes/codes.htm
As I mentioned previously, use the "search" function. I found these in about 3 minutes.
http://www.corvettebuyers.com/c4vettes/codes.htm
As I mentioned previously, use the "search" function. I found these in about 3 minutes.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
i'm one of the few people that have successfully troubleshot the 90-96 abs system as well as read the actual dealer manuals on diagnostics.
here's what i can tell you:
1. the codes can be wrong. yes i know that seems extremely weird but it actually can help you diagnose the problem. ghost coding is often a failed ebcm
2. the pumps almost never fail
3. there is a g sensor behind the radio the abs system uses. it's one of the reason the abs even on a 1990 corvette is better than say this newer interga i'm now racing. if this g sensor fails it will trip a code
4. you need an abs diagnostic scanner or if i remember right you can flash abs codes by jumping different jumpers on the scan port
5. if you get a failed wheel sensor code, replace it and still see that code you probably have a failing ebcm
6. those damn yaw - g sensors are hard to come by if you have a dead one
7. if you can get your hands on one of the dealer abs books they have troubleshooting schematics that can be helpful
8. if you have a pre 1990 car you NEED a breakout box to read codes...as far as i know
here's what i can tell you:
1. the codes can be wrong. yes i know that seems extremely weird but it actually can help you diagnose the problem. ghost coding is often a failed ebcm
2. the pumps almost never fail
3. there is a g sensor behind the radio the abs system uses. it's one of the reason the abs even on a 1990 corvette is better than say this newer interga i'm now racing. if this g sensor fails it will trip a code
4. you need an abs diagnostic scanner or if i remember right you can flash abs codes by jumping different jumpers on the scan port
5. if you get a failed wheel sensor code, replace it and still see that code you probably have a failing ebcm
6. those damn yaw - g sensors are hard to come by if you have a dead one
7. if you can get your hands on one of the dealer abs books they have troubleshooting schematics that can be helpful
8. if you have a pre 1990 car you NEED a breakout box to read codes...as far as i know
Last edited by racebum; Mar 17, 2011 at 10:48 PM.
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Burning Brakes
Joined: May 2010
Posts: 840
Likes: 4
From: High Point NC
I had the same problem. Pulled the codes and got that it was the right rear wheel sensor. It wasn't. My connector at the master is messed up and it would wiggle loose and when it lost contact the ABS light would come on. Drove me nuts because I had changed the master then installed the SS lines so I assumed that the code had to be right. I'm glad I didn't rush out to give someone $100 for a wheel sensor.
Double check that connector.
Double check that connector.
Thread Starter
Burning Brakes
Joined: Mar 2009
Posts: 830
Likes: 6
I had the same problem. Pulled the codes and got that it was the right rear wheel sensor. It wasn't. My connector at the master is messed up and it would wiggle loose and when it lost contact the ABS light would come on. Drove me nuts because I had changed the master then installed the SS lines so I assumed that the code had to be right. I'm glad I didn't rush out to give someone $100 for a wheel sensor.
Double check that connector.
Double check that connector.
Competing this weekend so will look at it during prep. If it's the wheel sensor it will have to wait until next week.
Have looked at the guides but haven't had much luck with the paper clip read the codes thing.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Pull the wheel sensors out and clean the "tips" (the pick-up pionts) of the sensors....start with the rear ones. The tips of the sensors are magnetic and small chucks of steel/debris will get stuck to them affecting the sensor's high/low funtion.
ABS Codes:
On the 1990 and 1991 model shorting pin "H" to pin "A" will cause the ABS light to flash ABS codes however there are four codes that will not display without the use of a scan tool.
ABS Codes:
On the 1990 and 1991 model shorting pin "H" to pin "A" will cause the ABS light to flash ABS codes however there are four codes that will not display without the use of a scan tool.
Last edited by engle1147; Mar 19, 2011 at 01:17 AM.
