ABS and TCS Help
Thread Starter
Pro
Joined: Apr 2007
Posts: 585
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ABS and TCS Help
Call me stupid if you must, but I can't find what I'm looking for when searching the threads on this forum.... 
I need help with a few things. I am getting service ABS and TCS messages on the DIC. I recently purchased my '98 coupe, and I was told by the previous owner that it is the right rear speed sensor causing the problem. I want to verify this for myself, however. If possible, I would also like to fix the problem myself.
1) How do I pull codes on the car?
2) Once I pull the code(s), where do I find a list of codes to know what it means?
3) If it is the right rear speed sensor, how easy is this to replace? I have been told that it is part of the entire hub assembly by a parts guy at my local dealership.
Your help is most appreciated,
LO PHAT
I need help with a few things. I am getting service ABS and TCS messages on the DIC. I recently purchased my '98 coupe, and I was told by the previous owner that it is the right rear speed sensor causing the problem. I want to verify this for myself, however. If possible, I would also like to fix the problem myself.
1) How do I pull codes on the car?
2) Once I pull the code(s), where do I find a list of codes to know what it means?
3) If it is the right rear speed sensor, how easy is this to replace? I have been told that it is part of the entire hub assembly by a parts guy at my local dealership.
Your help is most appreciated,
LO PHAT
Le Mans Master
Joined: Sep 2004
Posts: 5,707
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From: Los Angeles
Since you are a new C5 owner, the first question I have to ask is what size are the tires on the car?
DIC codes: http://www.stengel.net/diccodes.htm
DIC codes: http://www.stengel.net/diccodes.htm
Le Mans Master
Joined: Jul 2002
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From: Slave to the evil empire
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St. Jude Donor '04
Tech Contributor
Joined: Oct 1999
Posts: 40,999
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From: Charlotte, NC (formerly Endicott, NY)
Once you pull the codes you need to find somebody who will send you the diagnostics that go with each code. The lists of codes with a short one line description are incrementally better than useless as far as telling you what is wrong. All a code does is indicate a location in the car where an expected measurement was incorrect. The diagnostics provide a procedure that helps you find out what part failed. For instance the problem you talk about may not be due to a specific wheel speed sensor failing but a wiring problem in one of the connectors associated with that sensor or a problem in the unit that is reading the signal from the sensor, etc, etc, etc.
Bill
Bill
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Pro
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Thank you very much to all three of you for the help thus far! I just pulled the codes on my car. I will post them shortly.
The tires are all factory sizes on factory wheels.
LO PHAT
LO PHAT
Thread Starter
Pro
Joined: Apr 2007
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There were a lot of codes stored in this car ... LOL!
Here are the codes relevant to the traction control system. All of the codes ended in an H (if that "history" part is important in this case).
28 TCS Traction Control system ABS on page 5-86
- C1228 RR Excessive Wheel Speed Variation
- C1235 RR Wheel Speed Circuit Open or Shorted
- C1255 EBTCM Internal malfunction
If someone can point me in the right direction I would be most appreciative!
Thanks again,
LO PHAT
Here are the codes relevant to the traction control system. All of the codes ended in an H (if that "history" part is important in this case).
28 TCS Traction Control system ABS on page 5-86
- C1228 RR Excessive Wheel Speed Variation
- C1235 RR Wheel Speed Circuit Open or Shorted
- C1255 EBTCM Internal malfunction
If someone can point me in the right direction I would be most appreciative!
Thanks again,
LO PHAT
Tech Contributor
Joined: Oct 1999
Posts: 40,999
Likes: 9,764
From: Charlotte, NC (formerly Endicott, NY)
Do you have the active handling option on the car? That is RPO JL4 on the options list located in the glove box. I am out of town for a couple of weeks so can't get to my manuals but I would recommend you start with checking the grounds for the EBTCM first. You may have a rear mounted EBTCM if you don't have active handling. If it is rear mounted it is located near the diff on the left side of the car. It is attached to the brake pressure modulator valve which has all the brake lines going to it. If it is a front mounted EBTCM it will be located to the left of and below the power steering reservoir. It is always a good idea to check wiring connections and grounds to make sure they are in proper order before doing other diagnostics. In the meantime maybe somebody else with a manual can jump in with additional info such as ground points for front and rear ETCMs.
Bill
Bill
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Pro
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Burning Brakes
Joined: Jan 2006
Posts: 1,170
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From: Magnolia Greens NC
28 TCS Traction Control system ABS on page 5-86
- C1228 RR Excessive Wheel Speed Variation
- C1235 RR Wheel Speed Circuit Open or Shorted
- C1255 EBTCM Internal malfunction
If someone can point me in the right direction I would be most appreciative!
Thanks again,
LO PHAT[/QUOTE]
Wheel Speed Sensors
Code C1221 - 1228 indicate that one of the wheel speed sensors is either sending a bad signal or no signal. Start by checking the connections. The wheel speed sensors are integrated into the wheel bearing/hub assembly. The wire coming out of the back is the connection for the wheel speed sensors. Verify that the connector are not broken, damaged, or corroded in any way. Pay particular attention to the female end.
The wire coming out of the wheel speed sensor connects to and 18" jumper harness, then to the main harness. It is very common for people to have a weak female pin in one of those connections. If all of that checks out good, Swap the jumper harness from side to side. For example if the left front is bad, swap it over to the right front. and install the good one from the right front to the left side. Then clear the trouble code. If the trouble code is now on the right side, you know the wire harness is the problem. If the code is still on the left side after swapping the jumper harnesses, you know the problem is inside the wheel speed sensors.
If all the wires check out good, it's time to take a trip to Auto Zone for a new set of bearings. You can buy replacement AC Delco bearing from your dealer if you want to, or get the exact same bearing in a different box for half the price (~$150) from Auto Zone, you decide. The bearings should be replaced in axel sets, so if your left front is bad, you have to replace the right front too. While your at it, this is a good time to upgrade the lug studs and add spindle ducts.
- C1228 RR Excessive Wheel Speed Variation
- C1235 RR Wheel Speed Circuit Open or Shorted
- C1255 EBTCM Internal malfunction
If someone can point me in the right direction I would be most appreciative!
Thanks again,
LO PHAT[/QUOTE]
Wheel Speed Sensors
Code C1221 - 1228 indicate that one of the wheel speed sensors is either sending a bad signal or no signal. Start by checking the connections. The wheel speed sensors are integrated into the wheel bearing/hub assembly. The wire coming out of the back is the connection for the wheel speed sensors. Verify that the connector are not broken, damaged, or corroded in any way. Pay particular attention to the female end.
The wire coming out of the wheel speed sensor connects to and 18" jumper harness, then to the main harness. It is very common for people to have a weak female pin in one of those connections. If all of that checks out good, Swap the jumper harness from side to side. For example if the left front is bad, swap it over to the right front. and install the good one from the right front to the left side. Then clear the trouble code. If the trouble code is now on the right side, you know the wire harness is the problem. If the code is still on the left side after swapping the jumper harnesses, you know the problem is inside the wheel speed sensors.
If all the wires check out good, it's time to take a trip to Auto Zone for a new set of bearings. You can buy replacement AC Delco bearing from your dealer if you want to, or get the exact same bearing in a different box for half the price (~$150) from Auto Zone, you decide. The bearings should be replaced in axel sets, so if your left front is bad, you have to replace the right front too. While your at it, this is a good time to upgrade the lug studs and add spindle ducts.
Thread Starter
Pro
Joined: Apr 2007
Posts: 585
Likes: 2
Code C1221 - 1228 indicate that one of the wheel speed sensors is either sending a bad signal or no signal. Start by checking the connections. The wheel speed sensors are integrated into the wheel bearing/hub assembly. The wire coming out of the back is the connection for the wheel speed sensors. Verify that the connector are not broken, damaged, or corroded in any way. Pay particular attention to the female end.
You guys are the bomb!
I just put the car up on ramps, and I went through the process of checking all of the speed sensor connections. All of the connections looked fine, but when I was putting it all back together I noticed how close the right rear wire was to the wheel (as in almost touching). Further inspection revealed two things:
1) The parking brake lines appear to normally bolt to the bottom of the trunk tub. The lines on my car, however, were not attached there. I will make a quick trip to the dealer for the nuts that go on the bolts or find a suitable replacement for them.
2) The speed sensor wire was poorly attached to the parking brake line on the right rear. Because of this it had apparently been rubbing against the wheel. The flexible plastic wrap had burned off, and the wheel had rubbed right through the wire's insulation. I found a very small section of wire exposed.
I don't want to get too excited just yet, but I may get stupidly lucky on this. I wrapped the damaged section of the speed sensor wire in electrical tape, re-routed the wiring into a position further from the wheel, and then better secured the wiring to the parking brake line using more electrical tape. I took the car for a short five mile drive, and no warning messages or lights appeared on the dash.
I'll do a longer drive later today to be sure, but this might have been the problem. I'm guessing the exposed wire was shorting, grounding, or getting interference by rubbing on the wheel.
What do you guys think?
LO PHAT
Melting Slicks
Joined: Feb 2006
Posts: 2,938
Likes: 62
From: Columbia SC
Welcome to the madness. This is the best place to get information on your vette. I do not think I have had a problem that someone on this forum has not already had and was able to get it corrected with advice from these great members. 
Instructor
Joined: Feb 2008
Posts: 147
Likes: 1
From: Huntsville AL
Code C1221 - 1228 indicate that one of the wheel speed sensors is either sending a bad signal or no signal. Start by checking the connections. The wheel speed sensors are integrated into the wheel bearing/hub assembly. The wire coming out of the back is the connection for the wheel speed sensors. Verify that the connector are not broken, damaged, or corroded in any way. Pay particular attention to the female end.
The wire coming out of the wheel speed sensor connects to and 18" jumper harness, then to the main harness. It is very common for people to have a weak female pin in one of those connections. If all of that checks out good, Swap the jumper harness from side to side. For example if the left front is bad, swap it over to the right front. and install the good one from the right front to the left side. Then clear the trouble code. If the trouble code is now on the right side, you know the wire harness is the problem. If the code is still on the left side after swapping the jumper harnesses, you know the problem is inside the wheel speed sensors.
If all the wires check out good, it's time to take a trip to Auto Zone for a new set of bearings. You can buy replacement AC Delco bearing from your dealer if you want to, or get the exact same bearing in a different box for half the price (~$150) from Auto Zone, you decide. The bearings should be replaced in axel sets, so if your left front is bad, you have to replace the right front too. While your at it, this is a good time to upgrade the lug studs and add spindle ducts. [/COLOR]
The wire coming out of the wheel speed sensor connects to and 18" jumper harness, then to the main harness. It is very common for people to have a weak female pin in one of those connections. If all of that checks out good, Swap the jumper harness from side to side. For example if the left front is bad, swap it over to the right front. and install the good one from the right front to the left side. Then clear the trouble code. If the trouble code is now on the right side, you know the wire harness is the problem. If the code is still on the left side after swapping the jumper harnesses, you know the problem is inside the wheel speed sensors.
If all the wires check out good, it's time to take a trip to Auto Zone for a new set of bearings. You can buy replacement AC Delco bearing from your dealer if you want to, or get the exact same bearing in a different box for half the price (~$150) from Auto Zone, you decide. The bearings should be replaced in axel sets, so if your left front is bad, you have to replace the right front too. While your at it, this is a good time to upgrade the lug studs and add spindle ducts. [/COLOR]
More background- I've had the car about a month and a half (and it's my first :o ). Four days after purchase I had to put car in shop for transmission replacement and asked them to look at TC/ABS system as I had intermittently gotten error message during first 4 days. They said Right Rear hub/sensor assembly so I told them to fix it. Now, several weeks later, while on way back from 6-hour each way trip I start seeing strange instances of "ABS active" eventually followed by "service ABS/TC". Only code present is 1228.
Also, while looking through documentation in glove box I see where previous owner had this exact same part replaced not all that long ago. So, it seems to me that the root problem is obviously not the hub/sensor itself. Possibly the connector, possibly a wire in the harness? One thing I noticed yesterday that may be relavent to diagnosing problem is that the problem shows up usually when I'm making a sharp turn, not while going straight.
About to go take a look at car and will report what I find.
Thanks.
Instructor
Joined: Feb 2008
Posts: 147
Likes: 1
From: Huntsville AL
Well, I pulled the wheel and looked at harness. Nothing obvious- the harness wires were still inside of the plastic protective covering (can't remember what it's called). And harness was attached to the parking brake line as intended. I disconnected the harness connection from the hub and didn't see anything too obvious. So I did 2 things-
1. I used a piece of metal with a sharp point to try to bend the metal contacts (on the car-side connector) to make sure they were making good contact with the pins on the hub-side.
2. There was a grounding lug there on the frame so I took that apart and made sure the contact surfaces were clean. Didn't really look bad but I took some sandpaper to both lug side and eyelet connector to be sure.
I put all back together and drove about 15 miles (mix of around town sharp turns and highway) and had absolutely no problems. So I'll see how long my fix lasts compared to the dealerships $300 fix.
1. I used a piece of metal with a sharp point to try to bend the metal contacts (on the car-side connector) to make sure they were making good contact with the pins on the hub-side.
2. There was a grounding lug there on the frame so I took that apart and made sure the contact surfaces were clean. Didn't really look bad but I took some sandpaper to both lug side and eyelet connector to be sure.
I put all back together and drove about 15 miles (mix of around town sharp turns and highway) and had absolutely no problems. So I'll see how long my fix lasts compared to the dealerships $300 fix.