Mechanics

THE ABS,TRAC OFF, AND WRENCH LIGHT ARE ON??

2001 Chevrolet Cavalier • 11,300 miles

The abs, trac off, and wrench light are on. Which is a abs problem and its a rear sensor but inhave replaced both sensore and the harness on the axel and still on. What eles could it be?
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Doniadams
September 2, 2012.



Have the diagnostic fault code read and erased.

Caradiodoc
Sep 2, 2012.
It comes right back on as soon as earsed

Tiny
Doniadams
Sep 2, 2012.
Couple things to consider. First of all, fault codes never say to replace parts. They only indicate the circuit or system that needs further diagnosis. In your case, replacing the sensor and the wiring harness would probably solve that code 80 percent of the time. You also have to consider a computer problem, or more commonly a corroded connector pin or break in the wires anywhere between the sensor and computer.

The second thing to be aware of is there is one model of scanner that has a mistake in the software and it reads codes and data for the wrong wheel. It seems to me that was on a GM truck but I can't remember for sure.

You can use a scanner to view live data during a test drive. That will allow you to see the wheel speeds the computer is seeing. If they all seem to be correct, suspect a cracked tone ring. That will cause one extra pulse per wheel revolution which will set a code. I can not find much information on ABS for your year and model so you'll have to see what kind of tone ring is used. GM used a lot of speed sensors built onto the backs of the wheel bearings as an assembly. Those give a lot of trouble when a little, normal play develops from wear. The dealer's scrap metal bins are loaded full of them. It is not uncommon to have problems in as little as 15,000 miles. If your car has a normal external tone ring like everyone else uses, you can look at it to see if it is cracked between two teeth.

Another approach is to go right to the ABS Computer, disconnect the plug and measure the sensor's resistance right from there. You'll need the service manual diagram to figure out which two wires to measure across. A typical sensor will have somewhere around 500 to 900 ohms of resistance. If it's higher than that, or you find an open circuit, measure right at the sensor. If it's okay there, you have a break in one of the wires going to the computer.

You can also measure the AC voltage at the connector that is developed when you spin that wheel by hand. The voltage isn't accurate but all you're looking for is something vs. Nothing.

Caradiodoc
Sep 2, 2012.
What are the codes present?

KHLow2008
Sep 2, 2012.
C1234 LR sensor open/short

Tiny
Doniadams
Sep 5, 2012.
That is the Left rear sensor and the code means it is either shorted to batteery voltage or ground or has an open circuit. Since you ahve replaced the sensors and it did not work, it means you have a fault with the wiring. You need to test the wiring between the sensor and ABS control module to confirm whether it is an open or shorted circuit.

KHLow2008
Sep 6, 2012.