So, if you can get a CAN analyzer on the system when it happens, you can see if/when the ABS token goes missing (and/or if the entire bus goes down, but that seems quite unlikely since many, many other things would happen). I suppose it's possible that the ABS token is not actually missing and that the ECM does not recognize it for some reason, though it still seems more likely that there is some connectivity issue or board issue with the ABS module. If you still saw the ABS token during this time, it would rule out ABS token transmission as the cause, refocusing on ECM reception of that token.

Note that since you analyze from the OBDII port (at the far end of the CAN bus), if you still see all of the messages, that is a pretty solid indication that the CAN bus electricals are okay, and it's one of the modules.

On the CAN bus, the ABS token id is 0x7D3h. the message on each transmission is hex 14, binary 10100 (XK8 is the leading 1, 100 is the revision). It should be transmitted approximately 5 times a second to tell the system the ABS module still exists. The ECM token id is 0x7D0h just for comparison, INST token id is 0x7D2h and the TCM token id is 0x7D1h.

So, if this is possible, you are able to check, all at once:
1. CAN open circuit (terminator is in the ABS, so if that disappears, it will be obvious in the loss of messages, generally)
2. CAN short circuit (same as with 1.)
3. ABS/TCCM failure, because you lose the ABS token id in the CAN bus stream.
4. Some partial ECM failure, which you can suspect if the ABS token still appears 4-5 times a second, but the ECM didn't 'catch' it giving you the lights and code.

 

If time is an issue ( tick.... tick..... for mental sanity) it is still possible to get replacement modules so long as you get the right module for the car... hence the need to have the VCAT label

 

Or drip ... (long time later) drip... (long time later) drip. Still have one of these myself. Replacing the ECM soon. Since mine appears to be heat related, all victories are provisional heading into winter.

Mad Hatter, Is this happening every time you turn the car on, or intermittent? Does it happen after car reaches temperature or on the first ignition or on position?

 

@crbass I don't know the history of the car but i suspect that this has been to many a mechanic over the past couple years to try and resolve this problem and the PO ultimately passed it on to different enterprising indie mechanics that failed to fix it and then were unable to register the car with the government, and then it gets passed on to the next person.

Since I have gotten the car, it was intermittent and i wasn't able to establish a pattern for why it was turning on, although i can say it waited til it got warm at least twice while driving it.
Then I started trying to fix the problem, removed the abs module and had it repaired by a company. The car drove its furthest distance since I owned it with no problems, 40 miles out to get korean fried chicken. I parked it for the night and went the next morning to take it to get it smogged, i was sitting in a fast food joint and decided to try and read the smog check report with my bluetooth obd2 scanner, all of the christmas lights for abs came back and now they say P1637.

Since I got the P1637, the company that repaired my module sent me the module off of their test car and took my module again for testing. Both modules appear to be working perfectly on their car, and have a 100% failure rate with key on on my car.

The only thing that makes me uneasy is that it is the wrong module for my car, someone had replaced the pump and module with the wrong module #. The module repair place claims that it should be fine and that he tests all of his customers modules ( all model years ) on his own personal car and never has issues with incompatibility. ( I can't really back up his claim, and in the sake of scientific method it somewhat annoys me he didnt give me the correct model # module to test my car, his reasoning for not doing so was that it drove for 40 miles on my repaired incorrect module and that is an indicator it is not an incompatibility problem ).

 

So, in my experience, the ABS light (and occasionally assorted messages on the instrument panel) comes on when the car is on while I query the ABS module with my OBDII reader (Foxwell). It then goes off when the query is done. It does not set a code for me, however. In my car, the CAN token appears to miss about 1 cycle (~200 ms) at points during this stream. As for other OBDII scanners, who knows? Likely depends on what set of commands is sent.

As you note, perhaps not the most scientific module incompatibility test ever, but the code, taken at face value, suggests that either the ABS is not sending or not able to send its CAN token to the ECM or the ECM is not receiving/processing the CAN token.

What is the part number that is on your car vs the VCATS in the trunk?

Also, do you need this for the state inspection? Around here (NC), I don't think this is an issue if the brakes work, and there is not "some big grinding noise" (quote from the mechanic doing the inspection yesterday).

 

Maybe I will try clearing codes and then removing the obd2 adapter and driving it for a little bit and seeing what happens?


The part on my car is LNC2210AD, according to the vcats label it should be......... my vcats label does not list what it should be, but i called the dealer and they said my car was equipped originally with a: LNC2210AD. Which confuses the hell out of me because the module repair shop had told me it was the wrong part, but according to the diagram on their own website, my module fits my car correctly.


Yes I have to smog the car to title it. To smog it, i have to have no check engine lights on, the car has to pass its own internal smog test, and then they run it on a dyno for up to 45 minutes simulating a variety of different driving conditions to measure the exhaust output.

They actually never perform a safety inspection as far as i know.

 

I'd try that.

Yes, that part appears to be right for your car.

A rapid perusal of the internet suggests that an ABS light alone will not fail the California smog test. You'd need a check engine light and/or an emission code. E.g. look down the page

https://www.smogtips.com/forums-failed-smog-2.cfm

Of course, this is not an official opinion, but I know this is true for NC emissions/safety and "the internet" suggests it's true for CA.

 

That would be correct, if the P1637 did not also trigger the check engine light and poor engine performance.

It will not pass the emissions testing right now due to reduced idle performance, and the check engine light being on.

 

Are you sure that's the only code? The connection of the ABS system CAN token and idle/engine performance seems unlikely/unclear.

Do you have an OBDII scan with IDS or dealer/independent scanner?

 

I definitely don't have a known variable as for the scanner, it is a bluedriver bluetooth scanner.

It is questionable as to what it truly supports, I have a little bit of faith in it as it told me about a C code and a P code so far. My understanding is that most of the cheaper scanners don't cover any of the C codes, is that correct?


I have definitely wondered if a more proven scanner would reveal other issues, or more precise instruction as to my current issue.

I can definitely say that the check engine light relates directly to the ABS Traction control lights as they all illuminate and extinguish at the same instant. It is possible they are both symptoms of another problem, what that problem might be escapes me unfortunately.



As for the idle performance, it may just be wishful thinking, the DTC error list says that you can expect deteriorated idle performance when the car exhibits this code. The car has been hit or miss as far as engine balance and noises are concerned. Could be the ecm learning constantly from me removing the battery cables often, it could be related to this error code, it could be that my timing chain tensioner guides are likely located in my oil sump. It's on the to do list. I wouldn't put much thought into this until I have replaced tensioners and driven the car with no check engine lights for a while.

 

I'd see if I could get someone to use "Dealer level" equipment for a full list. Is your bluetooth scanner Jag specific?

Do you use the procedure for relearning idle after removing the battery cable?

e.g. https://www.jaguarforums.com/forum/x...re-how-138974/

 

The scanner is definitely not jaguar specific. I was surprised it picked up the C1137 code that it did.

I remove the battery cable every time i work on the electrical system, which is multiple times a day at the moment.

I haven't done an idle relearning, no. I will have to look up the procedure, for when I think the battery cable will be connected in a more permanent capacity.



I will have to take the car in to somewhere I can get it scanned with better equipment.

 

The procedure is in this link from above:

https://www.jaguarforums.com/forum/x...re-how-138974/

It's simple and takes 10-15 minutes. You might want to do it every time (at least the first bit) to avoid various idle hijinks.

 

I cleared the codes with my scanner and quickly removed it from the diagnostic port.

I drove the car the past couple days probably about 50 miles and the check engine light hasn't come on again.

I think the check engine light and CAN bus code was being thrown by the scanner disrupting the bus itself.

I am going to go try and get the car smogged and then I will try to figure out why the car is still pissed off about the ABS TRAC system.


The local San Diego jag repair shop told me that the 97 model year XK8 is very finicky with scanners and even among the scanners he has, one of them is unusable on that year car without triggering a check engine light.


The scanner that I am using is a Bluedriver OBD2 bluetooth scanner. I likely paid $100 for it just to spend days of my time, and hundreds of dollars in diagnostics, trying to figure out why my check engine light was on.


EDIT:

Just went to go take the car to the smog shop and the check engine light was on with key on again. I hadn't had the code scanner plugged in for a few days now so that definitely isn't what is generating my can bus failure. I plugged it in and scanned the code again and it returned the ole faithful P1637.

 

Did you have the jag shop scan it?

It seems like you must have another/other code(s), other than the P1637 if the instrument panel is apparently telling you that ABS TRAC is unavailable (?) while the CEL is off, then the CEL comes on later. Did you get the ABS TRAC message (and the ABS light) constantly during the 50 miles the CEL was not on?

Keep in mind, depending on what the CEL is responding to, it may take some drive time to show up. For example, if you don't get code P1111, it hasn't cleared everything through the cycle yet.

 

I have an appointment with a Jag specific scanner next Tuesday.

I suspect my scanner isn't telling me what is actually wrong with the car.

I also came to the conclusion that the check engine light and ABS TRAC lights are not joined at the hip.

The ABS TRAC lights were on the entireity of the drive duration where the check engine light stayed off for two days.

 

I had the jaguar mechanic scan the car and he didn't turn up anything different than I did with my crappy bluetooth scanner. He used all of the scanners that he had including IDS.

The mechanic had a 97 as his own personal car, he pulled the ECM out of it as it was known working and installed it into my car and it still turned up a P1637 indicating ABS CAN Failure.

I also managed to get the correct model # ABS module from the repair shop and installed in the car and it instantly reported the same P1637 code.


I honestly don't know what to do at this point.

What are all of the things that could cause a P1637? I am stuck with a car right now that I can't legally register in this state until I resolve this problem.

 

Old cars are notorious for bad wiring which is especially important in a CAN bus network. If you’re sure the ECM and ABS module are good, check the wiring harnesses pin by pin for continuity.

BTW the TCCM module is also involved. If the harnesses are good, then check this other module.

Don’t give up, you’re doing the right things!

 

Old cars? This is the newest vehicle that I have ever had haha. I have never had to deal with electronics before really.

I have already checked all of the CAN BUS wires in the engine bay at each plug for continuity, and also checked their resistance and voltage readings from end to end of the network.

The wiring diagram appears to show that the TCCM is T'd into the can bus wires between the ABS and ECM. What makes you believe that the TCCM could help trigger the P1637. My reason for asking is that if you know how, maybe that can help me to diagnose it's interaction with my problem.


I think the only two circuits that interact with the ABS module that I haven't confirmed are working as expected is the brake switch and the brake fluid level sensor.

 

The bus goes through each module. Looked at another way, each module is hanging off of the bus. ABS/TCCM on one side, INST on the other with the ECM, TCM and illumination module (passive) in the middle.

It's not clear that investigation of the brake switch or brake fluid level sensor would help. There are 4 things listed that can cause your code.
1. CAN open circuit, which you have checked, I think.
2. CAN short circuit, which you have checked, I think.
3. ABS/TCCM failure, because you lose the ABS token id in the CAN bus stream. This does not have to be all the time, could be intermittent. In other words, there could be a time during which the CAN message is not sent, but it sends all the rest of the times. It also could be that it never gets sent at all. I don't know of a way to check this other than looking at the ABS token in the CAN stream and seeing if it disappears. Or replace the module. It's unlikely that a new one would have an intermittent CAN token (or no CAN token). Frankly this would still be my guess even though you replaced the ABS module (temporarily?).
4. Some partial ECM failure, which you can suspect if the ABS token still appears 4-5 times a second, but the ECM didn't 'catch' it giving you the lights and code. Again, the only way to catch this is to determine the answer for 3. If 3 is not true (ABS failure), the 4 must be true.



Not clear what to do with the information that both the ECM and ABS modules were replaced and the code still remains. Were there any other codes during this time? This is important. I can walk out right now, disconnect the instrumentation module for a few seconds and get a P1637. And a host of other codes. And that had nothing to do with the ABS or the ECM or anything other than 1. above. But I can tell this general CAN failure from the rest of the codes all complaining that the bus connectivity was gone.


On its face, this appears to be a CAN problem. I'm also not clear what caused your check engine light. I don't think this does it. What were the other codes other than the P1637 for the check engine light?