My apologies if this not the correct thing to do but my frustration with this issue is being increased by the number of threads that I've posted to regarding the problem. I completely understand if this thread is taken down by the moderators.

I'll start from scratch. I bought this '01 XK8 convertible about 6 months ago. It ran fine but did give me several messages in the dash regarding the trac system, gearbox and a couple others. These were intermittent. There was, nor is there now, any check engine light.

I put my OBD2 on it and got a code telling me that there was an issue with the throttle motor relay. After changing it out the relay and clearing the codes I have been unable to get the CAT and Component monitors to clear. I also began to get codes P1797 and P1799 which, as I understand it, deal with the CAN bus connections between the Transmission Control Module and Engine Control Module.

After running fuel trim numbers a member seemed to think it may have been the O2 sensors so I changed out the downstream ones. I also did a hard reset by disconnecting the battery cables and holding them together.

I now still get the 1797 and 1799 codes, no engine light, and INC for the CAT and Component monitors. I have gone through numerous drive cycles that have been suggested here, in Jaguar documents and, of course, but every "expert" on the internet. None of them have cleared the monitors. I've put more than 500 miles on the car since clearing the codes.

It appears, from the type of connectors holding the catalytic converters onto the exhaust manifolds (bolts coming from the top of the manifold into threaded holes in the cat flanges rather than studs in the cat flange with nuts above the manifold) and what appears to be a replacement TCM (when I opened the compartment I found the TCM just sitting there, not in the slot it goes in, and hand written notation of the VIN in magic marker) that someone has been working on this car at some point. I'm not sure why the convertors would have been replaced at 63,000 miles but that's what was on the car when I bought it.

I've been told by members on here and the other Jaguar forum that the TCM/ECM faults would have nothing to do with the monitors not clearing.

Are any of the folks here who are experts in the area of Jaguars familiar with any method, other than "drive cycles", to clear these monitors?

I have about 2 weeks left to get this thing through a smog certification, which, in California, means the monitors need to read OK.

Thank you for any assistance,
Joe

 

I'll chime in (noting that saying that opinions are like ***, everyone's got one)

It seems from your posts that someone has replaced the cats (given the replacement of mounting studs with bolts) and the TCM (which is not a common replacement item, so a bit surprising....).
So something was likely wrong with the cats at some point....
Cats will be ruined if someone continually drives the car with excessive misfire condition, so mileage is no indication of good cats.
Given you have only owned the car for 6 months, do you know if the CAT monitor has ever completed (versus incomplete) whilst in your ownership? Otherwise:
- if could be that the replacement cats were bad when you got the car (damaged or blocked)
- it could be that the replacement cats don't even have cats in them - they could be cheapo deleted cat straight through pipes to make the engine run and dump the car on the next unsuspecting owner
- etc. more endless theories....

If the replaced oxygen sensors are not throwing any codes, it is entirely possible that the reason the cat efficiency test is not completing is because the cats are failing the efficiency tests - i.e. they are defective, as others have suggested
- of course if you replace ( them at huge expense) and then the efficiency test still fails you are going to be more than a little upset, so I understand why you want to eliminate other root causes as best you can , I would too

My best understanding (and opinions vary..) of the 2001 XK8 comprehensive component monitor test, is that it will not complete if any of the OBD2 Diagnostic Trouble Codes (DTCs) for the ECU are active, except for misfire (30x and 13xx series) or fueling codes (017x series) (which have their own monitor tests instead). I course I can't be sure.
- i.e. it will not clear/complete if any of the OBD2 DTCs listed in the AJ27 2001 OBD2 DTC summary document (as available at jagrepair.com, in the stickies large file section, etc.) are active.
I do not think that the transmission codes P1797 or P1799 are included in the comprehensive component monitor test (at least that are not for the 2001 XKR, because I have reverse engineered and reviewed the actual ECU software to some extent, and I would expect the XK8 to be similar), nor do I think any of the JAG (proprietary) DTCs are included.

So I do not think that the transmission DTC codes are linked to the catalyst efficiency test not completing.

Notwithstanding this, I do find the transmission codes a bit strange:
- I would have expected that if you have an active P1797 code, then the transmission would be in limp mode, and the car would display "Gearbox fault" or similar, so that is perplexing. If the code is pending (i.e. it happened once, but is not currently an active fault) then everything would be OK.
- I am even more perplexed by the P1799 code, if this was read from the ECU, since I did not think this was even supported on the 2001 XK8 ECU, only on later years (possibly it is supported and readable via the TCM...?).

 

Always, always check the condition of the battery FIRST!
What is the resting voltage of the car after it has sat all night?

This may not be your problem but it is so common we must start there.

Note the monitors are set by driving in the correct manner. They are NOT cleared. Every time you clear the codes all monitors are reset and you need to do the drive cycles you have read about to get them to set. I do feel for you because I have also driven hundreds of miles trying to get these to set! Sometimes it's just a royal pain.

No. There is no way to over ride the drive cycles and force the monitors to set.

Very confusing when you talk about the TCM? What compartment did you open? Can you post some pictures?
.
.
.

 

Hi Chirpy,

To the best of my knowledge the CAT monitor has never cleared while I've had the car. When I first got the car I recall there being a bunch of messages on the dash one of which was gearbox fault. These have all gone away after I replaced the battery.

I just completed the following:
1/ Disconnected the Battery
2/ Unplugged the cable from the TCM. Everything looked clean and no corrosion or contamination.
3/ Unplugged the 2 cables from the ABS. They were a little dirty on the outside but the pins looked clean. I sprayed them with contact cleaner and blew them dry and reconnected them.
4/ Unplugged the plug at the transmission port side that comes from the TCM. It was pretty dirty and covered with road grime and some oil. I sprayed both ends with contact cleaner and blew them dry and reconnected them.
5/ Reconnected the battery (when I first started it up I got some fault codes in the dash display - trans fault, trac fault etc.) but I shut everything down and restarted it and no messages)
6/ Cleared all the codes with the OBD2

I'm going to go for a ride and run the OBD2 when I get back and see what I get.

Are you aware of any test or measurement that would tell me if one or both of the cats are bad? I'm not getting any codes indicating that the O2 sensors are bad.

I did run a fuel trim test, which, according to another member on this forum, indicated that a downstream sensor was bad, so I replaced both of them while I was under there. I'm going to run the fuel trims again when I get back out to the garage. I'll post them when I finish.

Thank you for all the information. I really like the car but I'm too damn old to be dealing with this nonsense.

 

Hi Clubairth,

Sorry forgot to put that in. The old battery was testing out low so I installed a new battery a month or so ago. It's showing 12.6 volts when I check it first thing in the morning.

The Transmission Control module is in the covered section of the starboard side of the engine compartment against the firewall. Here are the photos. The first photo is how I found it. You can see it's just sort of sitting there. It was not in the slot that it is supposed to be in that holds it in place.

Joe

 

You might want to do some sanity checking on your CAN bus. There are 2 pins on the diagnostic port. Resistance should be 60 Ohm. It is accomplished with 120 Ohm at the ABS module, and another 120 Ohm at the instrument cluster. These 2 devices act as "terminators" on the bus. No good comes from a broken CAN bus.

There are TSBs describing a fix for known CAN problems stemming from bad soldering on the IC board. These could be fixed with basic soldering skills. Check jagrepair for all the TSBs. Take the listed VIN ranges with a grain of salt but I want to say MY2001 was part of the problem years for this part.

Best of luck, keep us posted.

 

Note that for most OBD2 diagnostic trouble codes, they will not show up until 2 drive cycles (engine on, drive the car, engine off, wait a bit, repeat) have been completed.
- the same fault needs to be detected on 2 consecutive drive cycles for the fault to be active, and the check engine light / engine malfunction light (CEL/MIL) to be illuminated

I'm no expert on diagnosing Cats, so I would defer to others on that...
- I have read that blocked Cats can be diagnosed with a heat gun (hotter upstream than downstream, which is the opposite of what should occur if operating normally), or a vacuum test while raising rpm and observing rate of change of vacuum, or...
- poor cat efficiency seems to be more challenging to determine - possibly some of the other thread comments on reading the downstream O2 sensor voltage might be illuminating, but I have no experience there. It seems more elaborate testing equipment is likely needed
- maybe if you can persuade/pay someone to do an emissions test regardless of the OBD2 state, and get the results, even though the cat test is incomplete, it might provide some data on how well the cats are doing their job, or not. (HC, CO, CO2, NOx levels)
- I don't know whether fuel trims shed any light on cat efficiency, especially since the trims to my understanding are primarily determined using the upstream O2 sensors, which are located before the Cats
- sorry I can't help more there.

Nevertheless, if the oxygen sensors are all working (no codes), and you have driven 500 miles, then it seems to me that the cats have to be a top suspect (if not the only one). Obviously the multiple ECU resets and code clearings that you have necessarily done in those 500 miles reduce the confidence in that diagnosis, but the possibility remains.
- the fact that cats are so expensive, and that no-one is officially allowed to sell used ones (because they are so expensive...) is a real drawback to deciding the best course of action (trying to fix it, or pass it on to the next guy).
Very tough call at this stage.

 

Excerpt from my MULTIPLEX ADVANCED DIAGNOSTICS training in 2002.

The entire STUDENT GUIDE is a large file but this is the CAN bus generalization.

 

 

Thank you motorcarman,

My lack of knowledge in acronyms fails me again.

In the CAN Network Communications Functional Check section what is the WDS?

Joe

 

https://www.jaguarforums.com/forum/g...d-truth-32683/

First there was JDS, then PDU, WDS, IDS and the one I never used............... SDD.
Jaguar Diagnostic System
Portable Diagnostic Unit
Worldwide Diagnostic System
Integrated Diagnostic System
Symptom Driven Diagnostics

 

So basically an OBD2?

 

To check the CAN bus has 60 ohms across it, you need to put a multimeter in ohms mode across pins 6 and 14 on the OBD connector by the driver's knee. The ignition should be off with the key out when testing this. Some forum members have bought themselves breakout dongles to make this easier, like this one (random example):-

https://www.ebay.com/itm/375616562288

The CAN bus working on not doesn't really impact on the O2 sensors as they connect straight to the engine control module, but I would still check it. It does seem that you are getting to the point where either you simply haven't driven the car enough to get the monitors to complete, or the cats are bad. There isn't much left to replace on the car now.

 

OBD II is essentially only about emissions and related items. Mainly one module (the PCM, often called ECM by Jaguar) and maybe a tiny bit of the TCM.

OBD2 is mostly read-only i.e. doesn't reprogram the module.

Full dealer tools cover all or nearly all of the car - say 10+ more modules - and can reprogram modules. Also, sometimes can force actuators to do things i.e. you can tell the tool to control devices. (Use with caution, preferably not at all!!)

If using a dealer-type tool it is wise to read up a lot, especially on the risks and requirements (such as mega dutuy power supply), and only use it to read data.

 

Hi Dibbit,

Thank you for the information. I have my old OBD2 scanner that I can cut up if it's too difficult to locate the pins on the port.

As I've said I'm reading/watching all kinds of threads and videos related to clearing these codes so I can get this thing to go through the smog check. Some threads have said that all trouble codes have to be cleared before the drive cycles will reset the monitors. I originally read threads that said it wouldn't matter unless the trouble codes were related to the emissions (O2 sensors and such) which I do not have. However, I figured I can't go wrong if I do clear these TCM/ABS/ECM/CAN issues and then do the "drive cycles". So that's where I'm at with this thing now.

I also received this as a suggestion to test the CAN :

 

OK, assuming I have to replace these cats. How can I actually know which one is bad? Is that heat test, where you measure the temp of the area before the cat and then the area after the cat and see what the difference is, the way to do it? Or do you just have to take them off? With all the wires, sensors, monitors and computers in the car shouldn't something pop up on the OBD2 or the car's little dash message screen that says "Hey, your bank 2 CAT is bad!"

Another question regarding replacing the CAT. Since the only thing they do now at the smog station is check to see if the monitors are OK and not INC how does the car (and monitors) know if f there is a C.A.R.B. compliant cat on there or not? What exactly is being measured if all they check is the monitor and the monitor (wherever that is on the car) is simply looking for a working cat.

Please excuse the stupid questions but frustration and lack of knowledge and a specific method to fix a given problem is causing my brain to overload.

Joe

 

Hi Joe,

Sorry to join your thread late. We all feel your pain. These types of issues can be challenging to resolve.

Regarding your replaced TCM, one thing to check is that its VCATS version matches the ECM's. Below is a photo of a TCM with the part number and VCATS version circled in red. On this TCM, the VCATS version is 002. I have only seen 001, 002 and 003 on X100s. Check your ECM label to see if its VCATS version matches. Also check your VIN range at parts.jaguarlandroverparts.com to be sure the TCM part number is correct for your car:




The Workshop Manual contains Pinpoint tests for diagnosing specific DTCs.

Regarding your readiness monitors that will not clear, if the catalysts were underperforming, typically you would get associated codes like P0420 and P0430.

One thing worth checking, since you believe the cats were replaced, is to see if the downstream oxygen sensors were installed with spark plug non-fouler extenders to move their tips out of the flow of exhaust gasses. This is often done to prevent P0420 and P0430 from triggering, but could be preventing your CAT readiness monitor from completing.

I can't recall for certain, but the Comprehensive Component monitor may not reset until the Cat monitor resets.

I am attaching the DTC Summaries for your 2001 as well as a later document that has excellent information on how the readiness monitors work and drive cycles for completing the various monitors.

Cheers,

Don

 

Here's the ECM tag.



I am once again at an acronym loss on VCATS.

Joe

 

Hi Don,

Thank you for the reply. I just posted a picture of the ECM info tag. Not sure what numbers to look at.

I replaced the downstream O2 sensors directly in the port, not with extenders. I am not getting any codes from my OBD2 related to O2 sensors.

Thank you for the attachments. I'll go through them and see what I can come up with.

Joe

 

Is that what appears to be a VIN at the top of ECM label? SAJDA42C41NA19009? Is that supposed to be the VIN of the vehicle it was installed into? Because my VIN is NOT that.