Another GOOFY Warning Light
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
4WABS codes can only be pulled with an ABS-capable OBD-II scanner. These are considerably more expensive than the typical scannner used in parts stores. That means that AutoZone and the like will NEVER be able to pull ABS codes.
If you don't have the ABS codes, all you can do is guess as to the cause of the ABS warning light.
The rear diff speed sensor is probably the most common failure. It is a 10 minute job to remove and test or replace it including getting the wrench, crawling under the truck, then putting away your wrench. Probably enough left over time to get a cup of coffee or a drink, Parts cost is between $15 and $20.
During POST, the ABS computer performs static checks of each sensor (wheel or diff), the solenoid coils for each of the valves in the pump module, and any other DC powere component that can be tested in addition to typical computer self-tests. Any open (or excessively high resistance) electrical connection to one of the tested components will also cause the POST to fail.
There is an additional self-test that occurs when the vehicle is first moving. Details are hazy (reference materials are not on hand), but they do involve dynamic readings from the sensors and a very brief dynamic test of certain of the valve solenoids. Can't recall the initial ground speed that the test occurs at, but it's quite low.
A sensor may pass the static self-test but fail the dynamic test due to a marginal condition.
Individual sensors can be tested with an ohmmeter. Again, away from my reference materials...sorry, no exact details.
Steve
If you don't have the ABS codes, all you can do is guess as to the cause of the ABS warning light.
The rear diff speed sensor is probably the most common failure. It is a 10 minute job to remove and test or replace it including getting the wrench, crawling under the truck, then putting away your wrench. Probably enough left over time to get a cup of coffee or a drink, Parts cost is between $15 and $20.
During POST, the ABS computer performs static checks of each sensor (wheel or diff), the solenoid coils for each of the valves in the pump module, and any other DC powere component that can be tested in addition to typical computer self-tests. Any open (or excessively high resistance) electrical connection to one of the tested components will also cause the POST to fail.
There is an additional self-test that occurs when the vehicle is first moving. Details are hazy (reference materials are not on hand), but they do involve dynamic readings from the sensors and a very brief dynamic test of certain of the valve solenoids. Can't recall the initial ground speed that the test occurs at, but it's quite low.
A sensor may pass the static self-test but fail the dynamic test due to a marginal condition.
Individual sensors can be tested with an ohmmeter. Again, away from my reference materials...sorry, no exact details.
Steve
Freshman User
Joined: Jul 2003
Posts: 41
Likes: 0
From: Euclid OH USA
Is it a coincidence that my ABS light came on shortly after the cruise control recall switch was replaced? Note that the switch was not propertly torqued and brake fluid leaked all over the top of the control unit. The service manager told me that the controller is sealed and water tight. I pointed out that the seals might not be compatible with DOT3, to which he had no answer........
Any thoughts?
Any thoughts?
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