Abs
Thread Starter
Pro
Joined: Apr 2001
Posts: 744
Likes: 13
From: Lenoir City TN
Abs
Once in a while it will come on for no reason. Sometimes when turning, sometimes when going straight. I searched the forum but found no answer. The fluid level is up. Its a 91 L98. I have a Helms manual and it does not address this issue, or at least I can't find it if it does. Went thru the "Flash Mode" to check for codes and it does not show any.
Any Ideas??
Thanks
Any Ideas??
Thanks
Le Mans Master
Joined: Jul 2002
Posts: 5,818
Likes: 2
From: Alive and well in Burlington NC
Do you get the ABS self test as soon as you hit ~4 MPH? You should hear a "moan" behind your seat and the ABS light should come on as the car hits that speed for the first time after every start. If it dosen't do that, it might self test at any time. I have the same issue now but just haven't gotten around to pulling the wheels and claening the wheel sensors (most likely cause of a sluggish ABS). If you do get the self test at start and it goes off again during the drive, there are other issues.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
At each wheel is a spoke wheel and a magnetic pickup. When the abs does not receive pulses when the car is moving, the abs comes on. You may have an intermittent coil or cable connection from the pickup.
Pro
Joined: Jun 2004
Posts: 646
Likes: 0
From: Santee Ca
It would be best to check the codes. I did and found that I need a new lateral accelerometer
My 90 the selftest light comes on when I first start the car. Then after a short time the light would come on and stay on. The code says lateral acceleromter voltage out of range. Has nothing to do with the wheel sensors. Lateral accelerometer cost over $250 at the dealer. Bought one from vette2vette for $50 including shipping.
My 90 the selftest light comes on when I first start the car. Then after a short time the light would come on and stay on. The code says lateral acceleromter voltage out of range. Has nothing to do with the wheel sensors. Lateral accelerometer cost over $250 at the dealer. Bought one from vette2vette for $50 including shipping.
Last edited by Insane1; Mar 23, 2006 at 09:19 PM.
Thread Starter
Pro
Joined: Apr 2001
Posts: 744
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From: Lenoir City TN
I've already checked for codes using the "Flash Method" shown in the Helms manual. There are some codes that cannot be accessed by this method though. The Helms says they can only be accessed with a "Tech One" tool that the dealers use. I may have to take it to one of them and see if it has any codes. If not, then it may be a loose or bad connection. I hate that, it could take hours to find.
Pro
Joined: Jun 2004
Posts: 646
Likes: 0
From: Santee Ca
From what I have read if you have an open or a short on any of the wheel sensors you will get a code set. Did you let the car flash for a bit? It flashes 12 three times before it does any more codes. You may also need to flash it with the car running after the light comes on. The code might clear itself when you turn the key off. My problem with my ABS was fixed today once I put in the new lateral accelerometer. On to my next project, getting the radio to work.
Le Mans Master
Joined: Jul 2002
Posts: 5,818
Likes: 2
From: Alive and well in Burlington NC
You can try to recover the codes this way:
Sequenced Code Recovery - 1990 through 1993:
With the interior redesign in 1990, Chevrolet added additional computer capability. The CCM (Central Control Module) was added and a method was provided to display codes on the speedometer of the Corvette.
From 1990 through 1993, you shorted ALDL pin "G" to "A" and turned the ignition to "On" without starting the engine.
This action will cause the speedometer and trip odometer to become a troubleshooting aid:
The codes will display on the speedometer. If there are no codes, the speedometer will show three dashes (---) and if the CCM cannot communicate with the other computers, the letters "ERR" will show up on the display.
The module number associated with the codes will be displayed on the odometer and will show which computer's codes is being displayed.
For the 1990 and 1991 Corvette, the modules are Module "1", the CCM computer and module "4", the ECM module.
Sequenced Code Recovery - 1990 through 1993:
With the interior redesign in 1990, Chevrolet added additional computer capability. The CCM (Central Control Module) was added and a method was provided to display codes on the speedometer of the Corvette.
From 1990 through 1993, you shorted ALDL pin "G" to "A" and turned the ignition to "On" without starting the engine.
This action will cause the speedometer and trip odometer to become a troubleshooting aid:
The codes will display on the speedometer. If there are no codes, the speedometer will show three dashes (---) and if the CCM cannot communicate with the other computers, the letters "ERR" will show up on the display.
The module number associated with the codes will be displayed on the odometer and will show which computer's codes is being displayed.
For the 1990 and 1991 Corvette, the modules are Module "1", the CCM computer and module "4", the ECM module.
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Drifting
Joined: May 1999
Posts: 1,478
Likes: 3
From: Sacramento, CA Money can't buy happiness - but it's more comfortable to cry in a Corvette than a Yugo.
Originally Posted by cshuman
Once in a while it will come on for no reason. Sometimes when turning, sometimes when going straight. I searched the forum but found no answer. The fluid level is up. Its a 91 L98. I have a Helms manual and it does not address this issue, or at least I can't find it if it does. Went thru the "Flash Mode" to check for codes and it does not show any.
The sensors are strong magnets that sit in the wheel knuckles and create an induced voltage as the toothed wheels on the axle or wheel bearing spin by. The front voltage is approx. 0.65vac and the rear is approx 1.1 vac. Small voltages easily affected. The openings that the sensors are mounted in are open to the road and can attract a lot of fine metallic road debris, distorting the magnetic field needed to create the sensor voltage. Each sensor is held in place by a small screw with a 10mm head. Pull each sensor and clean it with WD-40. Put a small dab of anti-seize on the sensor sides and reinstall. This may solve yur problem without going to a dealer.
Thread Starter
Pro
Joined: Apr 2001
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From: Lenoir City TN
Originally Posted by Mike_88Z51
The problem sounds like an intermittant issue. Generally the system appears to be working correctly and you have no codes. I'd guess that you might have debris build-up on the sensors themselves. This would cause the induced voltage readings to vary enough when turning or when you hit a bump to go out of spec for a second or two, setting the light.
The sensors are strong magnets that sit in the wheel knuckles and create an induced voltage as the toothed wheels on the axle or wheel bearing spin by. The front voltage is approx. 0.65vac and the rear is approx 1.1 vac. Small voltages easily affected. The openings that the sensors are mounted in are open to the road and can attract a lot of fine metallic road debris, distorting the magnetic field needed to create the sensor voltage. Each sensor is held in place by a small screw with a 10mm head. Pull each sensor and clean it with WD-40. Put a small dab of anti-seize on the sensor sides and reinstall. This may solve yur problem without going to a dealer.
The sensors are strong magnets that sit in the wheel knuckles and create an induced voltage as the toothed wheels on the axle or wheel bearing spin by. The front voltage is approx. 0.65vac and the rear is approx 1.1 vac. Small voltages easily affected. The openings that the sensors are mounted in are open to the road and can attract a lot of fine metallic road debris, distorting the magnetic field needed to create the sensor voltage. Each sensor is held in place by a small screw with a 10mm head. Pull each sensor and clean it with WD-40. Put a small dab of anti-seize on the sensor sides and reinstall. This may solve yur problem without going to a dealer.
Thanks!!!!!!!!
Melting Slicks
Joined: Nov 2002
Posts: 2,471
Likes: 2
From: 1993 Quasar Blue 'vert Scottsdale AZ
Keep it simple. I have found that just topping of the fluid doesn't make a big difference if the fluid is dirty. Flush the entire system and clean off the sensors.
Pro
Joined: Jun 2004
Posts: 646
Likes: 0
From: Santee Ca
Originally Posted by cshuman
Tryed the "A" to "G" test method, and have no codes. Any other idea's???
Thanks so much for the input!!!
Thanks so much for the input!!!
Thread Starter
Pro
Joined: Apr 2001
Posts: 744
Likes: 13
From: Lenoir City TN
Originally Posted by Insane1
I couldn't get the codes from the CCM. I had to go right to the ECBM to get the code. I will look at my book again and let you know which terminals need to be shorted to get the ABS light to flash the code.
I already did the ECBM checking for codes with non set.