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ABS Codes?


Well-Known Member
April 7, 2006
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City, State
Year, Model & Trim Level
98 XLT
Well I am still having ABS troubles, so I took the beast in and had it scanned...c1102,c1230, and c1237, all related to the rear wheel sensor...I replaced it again, disconnected the battery and its still on...what else could it be? I am going to ohm out the sensor tomorrow, but I've already changed it twice...I also replaced the harness (but I don't know which side of the harness wires goes to which color of the vehicle wires for sure, so I've tried it both ways...) Any help is appreciated!


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What is actually INSIDE the diff. there? I haven't really gotten much into the differentials much, so I'm not real familiar with what could be inside for the ABS.


PS Here is the definition of the codes:

C1102 ABS Acceleration Switch Circuit Failure
C1230 Speed Wheel Sensor Rear Center Input Circuit Failure
C1237 Speed Wheel Rear Input Signal Missing

Did you test the wiring right at the computer? I know that the harness was replaced, but if the computer doesn't see a signal from the sensor it will show a code. As for the inside of the differential, take off the sensor, and look into the opening. A part should move right near where the sensor is every time the rear wheels move. Jack up the rear wheels, put it into neutral, and the turn the wheels by hand. Look into the hole where the sensor goes.

There is a tone ring in the diff. If you break a tooth on that ring, it will throw a code. You aren't going to be happy if that's the case...

But I'm thinking along different lines here. Without the pinpoint tests in front of me, I'm just wondering if you have a harness unplugged or damaged. All codes seem to have something to do with underneath the vehicle. I would think a very careful inspection of the harness may show you something.

Edit: Can you get your hands on a Breakout Box adapter for the ABS and a service manual? Use those to check your circuits for proper readings.

Only problem I can see now is even if I clear the rear codes, I still have:

C1102 ABS Acceleration Switch Circuit Failure

Which is the g switch. Where even is the g switch? I have both the haynes and chilton's and it doesn't tell you...this is getting very irritating :(..

Also, I checked my wiring under the car, and I have the back of the actual sensor and I need to know which color wire goes to which side. There is a red and a green wire. My wiring harness was replaced by me, and I don't think I hooked it up right. With the prongs of the sensor facing towards you, is the left one green or red? Can someone check for me? I'd forever be in your debt. Thanks in advance guys!


Well, I switched the wires around, and the light was still on. So I drove it to work today, still on. On the way back home however, the light was on and then turned off. I made a stop (about 20 miles towards home) and went inside, left the car on. When I came back, the light was on again. I don't get this? Can someone check their wires for me?

Nobody can look for me real quick? I find that hard to believe! :(


The "G" switch on my 99 is located inside the left frame rail about half way down the vehicle.

You asked for someone to go look at their harness for you at 8:17 at night! Most folks are in for the night. Personally, I was watching Oregon State kick the snot out of USC! :D I wasn't about to get up and check wiring during that! Maybe someone can look this morning for you.

I have the green wire connected to the left wire, and red connected to the right if you are looking towards the rear of the car.

Hmm, isn't working AGAIN. Can someone crawl under the car and check for me please? I'd offer to paypal someone some money, but I don't have any :(


Well it's weird. I hooked it back up the other way, and now the light isn't on initally, I go to pull out of my parking space, and it goes on a few seconds after driving forward. But if I stop, put it in reverse, it turns off? Wtf? Also, I'm still not sure the colors are right.

Anyone out there that's helpful? :(

I guess not. Now I remember why I stopped coming here for a long time.

Anyone out there that's helpful? :(

I guess not. Now I remember why I stopped coming here for a long time.

Dude, you bumped the post at just before 1AM eastern time on a week night... At least half of the members on this board were in bed... and then you *****ed about it. Patience is a virtue. With an atitude like that, it's unlikely anyone's going to even try to help out any more.

You're facing a problem that very few people, if any here on this board, have had to deal with. ABS systems are quite complex, and often times beyond the diagnostic skills of most shade-tree mechanics.

It sounds like it could be a failed G-switch. It's on the driver's side frame rail, near the ground strap and fuel filter. The two nuts that hold it in place are on the outside fo the frame rail. Unfortunately I cannot find a connector pin-out diagram for that particular connector... No idea why it's not in the service manual.