I started getting the TRAC and ABS lights about a month ago, but they only happened every once in a blue moon. I daily drive my car, so that means in the rain too. Funny how a lot of these problems only happen in the rain...

The main time that I would see this ABS TRAC light combination come up was when I spun the tires a little in the rain just messing around. Usually it would come on and go back off after a few seconds. It started getting worse and worse, and now in the past week or so it pretty much has been coming on and staying on. I don't spin the tires on dry pavement because of the wheel hop and the risk of braking something. Only did that once since I bought the car and that was way before these lights started popping up.

I pulled the codes earlier and this is what I got:
TCS
C1223 H - LR wheel speed sensor is 0
C1291 H - Open brake lamp sw contacts during deceleration (??? WTF is this)
C1227 H - Excessive wheel speed variation
C1234 H C - Wheel speed circuit open or shorted (it should be noted that when I cleared this one in the DIC, the code popped right back up. It did this twice and will not go away.)

BO-RFA
U1096 H - Loss of communications with IPC
U1016 H - Loss of communications with PCM
U1064 H - Loss of communications with DCM (apparently my Remote Function Actuation System is an unsocial a**hole )
C2120 H C - TPM sys malfunction

(Seriously - my car has no tire sensors, hence the codes in the BO-RFA)

I have no idea what to do about the TRAC ABS problems though, so if you guys don't mind can you help me understand what is going on here? Please point me in the direction of any info on how to fix this. Thanks

 

Let's start with the easy one ....

C2120 .... If you have no tire pressure sensors, this will keep appearing .... simple as that. If your remote key fobs are working properly, the Uxxxx codes in the RFA can be deleted/ignored. What year is your car ??

C1223 H - LR wheel speed sensor is 0
C1227 H - LR Excessive Wheel Speed Variation
C1234 H C - LR Wheel Speed Circ Open or Shorted

I updated your description of the C1227 and C1234 to indicate which wheel it is for. Note that the three codes apply to the same wheel. Sounds like that sensor most likely has a wiring problem. Sometimes the car is getting no signal (C1223 and C1234) and other times the signal does not make sense because the wheel appears to be accelerating and decelerating by more than 10 mph in less than 0.01 seconds, and it has done it at least 3 times in less than 0.2 seconds (C1227).

Remove the rear left wheel, and inspect the connector for the wheel speed sensor. Look for corrosion in the connector. Also look carefully at the female side of the connector, often the "blades" that the male side slip between have moved and are not making good contact with the pins that insert into them. $20.00 says that will fix the problem.

C1291 H - Open brake lamp switch contacts during deceleration

The brake lamp switch is what turns on your brake lights ... but it is also monitored by some of the cars computers so they can perform functions such as turning off Cruise Control as soon as you step on the brake. The EBCM knows vehicle speed, and it monitors the brake lamp switch. If the EBCM sees the vehicle decelerating by more than 5 mph per second (along with some other parameters) .... the EBCM knows the brakes have to be applied (the engine itself can't slow the vehicle that fast) BUT if it doesn't see the brake lamp switch close during that deceleration it is programed to believe the switch has failed and sets the C1291 to warn of the failure.

First, test your brake switch. This is a complex test, so study carefully before trying this .....

Go out to car, step on brake pedal, have someone behind the car tell you if the lights come on .... alternatively have the rear of the car near a wall so you can see the reflection of the lights as they come on.

If they come on ..... no problem. If they don't come on either the switch is bad or there is a wiring problem.

NOTE: The Service Manual warns that wheel speed sensor problems can lead to the setting of C1291 ..... so if your lights are working this error may disappear after the C1223, C1227, and C1234 get fixed.

 

Thanks alot, this really helps. I'll pull the wheel off this afternoon if I get to it after work.

My car is a '99. I am aware that the C2120 code is because of no sensors. The previous owner told me the wheel sensors were not on the wheels because they are aftermarket 2K wheels and the sensors wouldn't fit. Unfortunately the error message cannot be programmed out using a tech II, and I just have to keep a really close eye on the tires.

 

ok guys, I did some work on the car tonight. I'm still getting C1234 H C. I found the problem though, low and behold...The ABS plug that attaches to the hub is connected to a littel metal piece by a clip. the plug had come off or had been removed previously for some reason or another, and the wires had been laying on the half shaft. the spinning shaft wore through the wire insulation and basically just did them in. So, after a little testing and checking I tried to get everything back going, but no luck.

I have a red and black wire coming from the car harness to the back of the female plug. on the male connector back side, the wires are both black....

I tested the harnes female conector with the gnition switch on and got -5v one way and 5v the other way. I guess that system works off of 5 volts...

The plug tested fine and everything looked good. one observation I made was that there was no resistance between the wires coming out of the hub, and I don't know if there should be. These would be the wires that go into the back of the male plug. I checked and double checked everything, and finally connected them. Not sure of the negative and positive orientation of the plug because both wires are black and they had worn completely in two. I checked it both ways with aligator clips, and cleared the codes both times an turned the ignition switch on and off. no luck either way. In the end I conected the wires in the orientation that they looked like they were in from the factory. I am pretty sure this is correct because they are so short I doubt they would have been crossed up.

I figured maybe it was still setting the code because the wheel had to turn first to reset it, but I drove around the block and still nothing. If I reset the code it comes right back instantly...

What else do I need to check....?

Electrical problems are such a PITA...The trac control being off is making the car get a little less gas mileage now too.

 

When you say ....

"The plug tested fine and everything looked good. one observation I made was that there was no resistance between the wires coming out of the hub, and I don't know if there should be"

The wheel speed sensor should have a resistance of between 850 to 1350 ohms.

Check it again to be sure, but if no resistance the sensor has failed.

You will need to replace the entire hub, the speed sensor is an integral part of the hub assembly.

Also, if you want to check the orientation of the connector, I'll give you the wiring for the Left rear and Right rear connectors.

Left Rear ...

BLACK is the signal and is the A side of the connector
RED is the reference (5 volts) and is the B side

Right Rear ...

BROWN is the signal and is the A side of the connector
White is the reference (5 volts) and is the B side

Let me know if you need more info .....

 

I am absolutely sure of this. I checked and checked and tried to get resistance out of the two wires coming from the hub and I got nothing. I guess this means time for new bearings....

Is this the reason it keeps setting the C1234 H C code? It makes sense if it is.

Oh well I guess it won't hurt, and maybe it will even help the gas mileage.

 

Yup, no resistance in the sensor is what is setting the C1234 .... replacing the hub will clear the problem and your system will work correctly once again.