Our 60K-mile 2002 VDP has been throwing the 'trac not avilable' message along with the ABS light sporadically for months. It usually clears on the next start-up and a couple weeks later throws the error again. Now it usually takes several start cycles to clear the flaw. I'm assuming some sensor is failing or has a poor connection, but have no idea how to track it down. Any suggestions from our amassed wisdom?

 

Cathead, just a note about this subject, you ahve posted it in the 2009+ XJ forum and not for the previous generation that would be the one relating to your car. Just an FYI.

As for your problem, odds are, you have an ABS/wheel speed sensor that is failing. This is causing the car to see 3 wheels spinning and 1 wheel sitting still (not in reality, but that is what the computer sees). This causes the car to see an error and disable the ABS system (hence the ABS light). Since the traction control is also seeing the one tire sitting still, it doesn't know what it should do as it knows there is a problem. So, this will throw the "Trac Not Avail" message to so you know as the driver that you won't be getting any assistance in less than ideal traction conditions. As for the solution, you should be able to connect up a code reader and read the coders. You may need a better than the minimum reader (like what is found at a lot of auto parts stores that you rent for free), but what you are most likely looking for is one of the following codes: C1145, C1155, C1165, or C1175. This will isolate the problem down to a specific wheel that is causing what you are seeing. From there, you have to look into whether it is bad wiring, a bad sensor, or there is an issue with the wheel bearing/reluctance ring.

 

Thanks, Thermo. I realized later I was on the wrong page, but figured the symptoms are probably similar. Your answer was very complete and helpful, thank you. I'll see if my code reader is sophisticated enough to do the job, or will find one that is. I appreciate you providing the codes; once I know where the problem lies I can deal with it. BTW, despite Jaguars having a spotty reputation for reliability, we have had a Majestic and five VDPs over the years (my wife won't drive anything else) and they have been very reliable and trouble-free cars, even into triple-digit mileage on a couple of them. Thanks again!

 

Cathead, let me know what codes you get. I have the tables that help narrow down what the possible problems are. I can help you get to the bottom of this. FYI, the codes for your problem should be locked into the ECU. So, you can read the codes whether the problem is in or not.

 

Thanks again for your offer to help, Thermo. My scanner came up with stored code P1111 and "definition not found--see Service Manual." Any ideas?

 

Cathead, P1111 is a code to say that everything is running as it should and that there are no error codes. This is where a cheapy code reader is making things appear good but they are not. Most cheap code readers only read P-codes. What is meant by this is P codes refer to the powertrain (hence the P). If you have a problem with say a wheel speed sensor, these are obtained by looking at C-codes (or chassis codes). This is where you may need to find a friend with a higher end code reader and have the codes looked at again. If you had a problem with a power loss to a computer, you would be seeing a lot more things going on with your car and you most likely would not be getting the P1111 code either.

If I had to take a guess as to what you will find, I would guess that you are going to find either C1145, C1155, C1165 or C1175. These are for the 4 wheel speed sensors which is what normally causes what you are seeing. I feel pretty confident in saying that you don't have a loss of the ABS computer as this normally results in the speedo dropping to zero (ECU looses its speed signal input from the ABS module). So, that is a good thing. It you had a problem with one of the steering sensors, you would only see the traction control message, not the ABS light. So, we can eliminate a few things from the car. Even if you had an intermittent issue where a sensor was lost and then came back later on in the drive, you should still have a locked in error code since you got the warning lights. The other thing that you may want to try is leaving a code reader plugged in all the time. There are codes that will come in for such a short period of time that they can trigger issues, but not lock in. These would be seen under "pending codes". Once you turn off the car, these pending codes get cleared. This is why you need to connect the code reader before you take the car out for a drive. that way, if your error comes in, you can leave the car running and then look at the pending codes.

Lets see what a better code reader says and then we can take things from there.