: ABS Wheel Speed Sensor Codes



FrankT
11-12-07, 12:39 PM
My 99 STS kept illuminating the ABS and Traction control indicators, along with those indicators I would get the check stability system message. I just kept clearing them till I had the time to go through the system and find out why. The most common factor here is the Right Rear ABS sensor and its circuits. The codes were consistent and intermittent, they were:

DTC C1224 RR Wheel Speed Sensor Input Signal is 0
DTC C1228 RR Excessive Wheel Speed Variation
DTC C1235 RR Wheel Speed Circuit Open or Shorted

The ABS wheel speed sensor is self generating sensor, meaning it produces an AC signal or frequency that the brake module uses to calculate the wheel speed. There are other sensors that have the same operating principles such as in the engine control system, the camshaft and crankshaft sensors, in the transmission vss, and output shaft speed sensors.
So, you guessed it, I started at the right rear ABS sensor, I didn’t want to spend $400.00 just yet for a hub and sensor, so I checked out the circuits first, my suspicion and hope was that there’s a poor connection somewhere between the sensor and module.

I have a Tech2 so I drove the vehicle back and forth to work for several days, but, wouldn’t you know it, the car would never act up when the Tech2 was connected to the vehicle.
1. I measured the resistance of the right rear ABS sensor; I found the resistance @1k ohms, this is within specs 850-1350 ohms.
2. I then measure the AC signal frequency from the sensor; I set my DMM to the mV AC scale, and spun the wheel as fast as I could. The reading was over 110mV, this is within specs, it should be at least 100mV.
3. My suspicion along was a loose or poor connection some where between the RR sensor and brake module. So, then I started checking the terminal connections the first circuit I checked was 882 the brown terminal, I did what we call a terminal drag test and found very little drag resistance one that terminal compared to the other one. Upon a close inspection I found that the terminal was spread slightly, I reached in there with a small pick and closed up the gap.
4. Bada bing, bada boom, been driving the car for 3 days now, no problems, no lights.

med
11-12-07, 07:40 PM
Thanks.:thumbsup:I have the same intermittant problem on my 1994 seville. I get codes T031 (RR Wheel Speed Sensor Fault) and T033 (RR Wheel Speed Sensor Continuity Fault) usually at start up, then they disappear for awhile. I originally thought it was weather related. I checked the connections visually but did not trace with DMM. It's sounds like the same problem. Just get the connector on there real good or what?

FrankT
11-13-07, 07:54 AM
Med,
Yes, make sure the connector is seated correctly, but more importantly take a good look and test for proper terminal contacts, inside the connector, make sure the terminals are not spread open too far, if they are, close them up some with a small pick. They should be clean and free of any corrosion too.
Becarful not to damage the small metal terminal contacts. Hope you find your ABS problem.
Frank
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Another note on the ABS Wiring:
The ABS wiring is shielded to prevent outside electrical interference on that circuit. Some electrical components/circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise and stray voltages. These types of wires can be repaired, but a special procedure must be used, if spiced incorrectly you will have problems. GM makes special pig tail repair harnesses, your best bet is to use these wire repair kits.

ewill3rd
11-13-07, 10:07 PM
When I see stuff like that I usually recommend installing what is called a "jumper harness".
This is a long segment of the special wire used for ABS systems with a nice shiny connector on the end that plugs into the sensor.
You work back into the harness as far as you can to a point where it is not subject to movement then you can splice the new harness into the existing vehicle harness.
When you see multiple codes like that from one sensor it is a good indicator that you have a harness or connection problem.

This kind of stuff shows up better if you use the "live plot" feature on the Tech 2.
Make sure to watch the road every now and then. ;)

FrankT
11-14-07, 07:29 AM
Couple of good points ewill, Thanks :yup:

I would have recorded the ABS data if the car would've acted up while the Tech2 connected to the DLC. The problem was very intermittent, as time went on it seemed to occur everytime I hit a bump in the road.

The Tech2 Live Plot is great feature, you can set up the Tech2 to take a snapshot automatically when a code sets or you can trigger it manually when ever you want. Once you have captured the data, graph it, the graph helps you see spikes and dropouts very clearly.

The "jumper harness" you are reffering to was the same thing I was trying to explain in post 3, but I called it a pigtail wire, thanks for making it a clearer and giving us the correct name. It always helps to call a component the by the correct name when going to the parts dept.

cadillac8686
11-14-07, 05:30 PM
I have an 02 STS with the same problem. I need to know what codes it would be so I can tell my warranty company. I cleared the so it has not came back up but the lights will not go off even when I clear the codes, they are alwayts on. I had it ran on the computer and it said it was the drivers side wheel sensor. I have already replaced the passenger wheel bearing. My car pulls to the right and it shakes when it goes 60 to 90 mph. I hate it.

urbanski
11-14-07, 06:25 PM
I have an 02 STS with the same problem. I need to know what codes it would be so I can tell my warranty company. I cleared the so it has not came back up but the lights will not go off even when I clear the codes, they are alwayts on. I had it ran on the computer and it said it was the drivers side wheel sensor. I have already replaced the passenger wheel bearing. My car pulls to the right and it shakes when it goes 60 to 90 mph. I hate it.

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