When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So it looks like my "VCATS" info from the TCM and ECM that are in my car would be:
ECM - LNG141OBD or LNG1410BD
TCM - LJE2401AB
Those are the part numbers. The VCATS may be printed with the part number on the component label, or at another location on the label. See the photo I posted in post #17 of this thread.
Here's the photo of Graham's VCATS label, showing the suffixes after each part number as Bob is describing:
In the example above, the part number of the Body Processor Module is identified as:
LJA 2500AG/055.
In the above, the basic part number LJA 2500AG has been programmed during vehicle
manufacture for the specific market and features of the vehicle concerned, and is identified as
/055.
This would be the complete part number for a replacement BPM for the vehicle concerned,
if it were necessary to order one from Jaguar Parts Operations. Note that the suffix /055 (in the example above) does not appear on the label on
the CM concerned. This number appears only on the VCATS label of the vehicle
The "wonderful" thing about Jag's modules is that, AFAIK, there is NO reference to the VCATS "version number" outside of that freaking sticker in the spare wheel well. Very few parts recyclers retain that information when scrapping a car.
If one's scan tool can communicate with a module, will looking at the internal module info yield the VCATS?
When looking up parts in JEPC, the module list states at the top line...................
USE THE PORTABLE DIAGNOSTIC UNIT TO DETERMINE THE PART NUMBER SUFFIX.
The parts dept would not order any modules without the part number and VCATS suffix.
I never bothered to use PDU, WDS or IDS to determine the VCATS suffix, I just read the label in the boot.
I'm not seeing any suffixes on the labels of the modules. Am I looking in the wrong place or am I just not seeing the suffix?
The only module with the VCATS version on the label is your TCM. The VCATS version is 002, as given at the beginning of the number above the lowest barcode.
When I get a parts car or if I swap in a used module to a customers car I print the suffix on the module's case.
I usually take a pic of the label and keep it with the title if it's my car.
It's just a habit I have in case the car goes away but the module remains.
While I'm not familiar with the term "kitbashing" I'll assume it has something to do with using non compatible parts on a car. I'm not sure what "marginally compatible parts" you're referring to. While I'll agree that someone has been working on this car who was perhaps not an expert in the area of XK8, or perhaps Jaguars in general, the parts that appear to have been worked on or replaced look to be proper Jaguar parts. Could you please let me know which parts you believe are "marginally compatible"?
Your analogy doesn't make any sense to me. No one would attempt or be able to install a 2 barrel carburetor on a "8 cylinder 4 barrel intake" manifold. It clearly would not fit. The same goes for the v8 intake manifold onto a straight 6 engine, it obviously will not fit. I see no indication of someone putting a part that does not fit onto this car. If you're referring to what appears to be the Transmission Control Module and Engine Control Module they are both plugged into the original cables. If it turns out that these are "marginally compatible" or non compatible parts and the source of the problem of not being able to reset the CAT monitor why would a company build a module that is not compatible with one model yet give it the exact same plug as that model? Especially if this module is part of a highly complicated computer system. Also, if these parts are the source of the problem then it is exactly the Onboard Diagnostic system that is the problem. These 2 parts are central to the OBD system.
These electronics modules may have connectors that match up and look the same on the outside, but if the electronics and code on the inside doesn't match that the ECM expects, they won't work properly. Just like mechanical parts that don't bolt up. Looks like you are on the right track with determining suffixes for what you have vs suffixes you need..
Last edited by MikeGriese; May 23, 2025 at 04:00 PM.
I don't see any function on my OBD2 that looks like it will be able to read what's inside the ECM.
I tried to find the company whose name is on that big sticker on the back of the ECM but it looks like they're no longer around. I call a Jag dealer up in the Sacto area but they couldn't help. They referred me to a guy who was supposed to have a good knowledge in "older" Jags and I called him. His contention was that since I'm not getting any codes from my OBD2 that it's just the finicky drive cycles that are stopping the CAT monitor from resetting. He's apparently worked on numerous XK8 and, according to him, they do have an issue with resetting that monitor.
I guess when the smog shop gets the car back they'll deal with it. If they can't get it fixed at least I'll have a shot with this BAR Referee.
They referred me to a guy who was supposed to have a good knowledge in "older" Jags and I called him. His contention was that since I'm not getting any codes from my OBD2 that it's just the finicky drive cycles that are stopping the CAT monitor from resetting.
It is quite possible that your car has stored Network-related diagnostic trouble codes that your scan tool cannot read. Most generic OBD2 scanners can only read Powertrain (P-prefix) codes. But your Jaguar can also set Network (U-prefix), Chassis (C-prefix) and Body (B-prefix) codes that can only be read by a dealer-level system such as IDS, or a high-end third-party tool like an Autel, Launch, Autologic, etc., or possibly one of the Jaguar-specific Foxwells or iCarsofts.
Network codes often relate to communication faults between modules. I do not know for certain, but it seems possible that if you have one or more modules with incorrect VCATS versions, some ECM or other module CAN communication faults may exist. CAN is Controller Area Network, the primary computer network by which many modules communicate, including the ECM, TCM, Instrument Cluster (IC), etc. I also do not know for certain whether such a fault could prevent the CAT monitor from completing.
My OBD2 is an iCarsoft LR V2.0 which is specifically for Jaguars and Land Rovers. I do get U codes (2500, 1261, 1135 & 1041) and B codes (2727).
I'm still trying to track down the full VCATS for the ECM. The car is still at the body shop. I'm going to see if they're open tomorrow and run by and take a pic of the label in the trunk with the VCATS numbers.
Well while I'm waiting for my car to get put back together at the body shop I went over and took a picture of the VCATS label in the trunk, which was located under the carpet on the port side of the trunk floor. Here's what it shows:
Now since my TCM has the VCATS number of LJE 2401 AB/002 it would appear that it is not compatible with this car. Is that correct?
The ECM has a VCATS number of LNG 141OBD but at this point I do not know what the extension is.
Could this be what the problem is with the P1799 - P1797 codes? Could it also be why the CAT monitor will not clear?
I've also just found out that the seller is responsible for making sure the car can pass smog here in California and I can take her to small claims court for what it costs to fix it so it passes. It is apparently pretty much a no questions asked ruling.
Now since my TCM has the VCATS number of LJE 2401 AB/002 it would appear that it is not compatible with this car. Is that correct?
Could this be what the problem is with the P1799 - P1797 codes? Could it also be why the CAT monitor will not clear?
It seems definitely possible that the incorrect VCATS version of the TCM is causing the P1797 and P1799 codes. I don't know if this could be related to the CAT monitor.
Is there a way to buy a matching TCM and ECM? How about a way to “program” or “reprogram” this TCM with the correct information? I’m still trying to find out how to determine the full VCATS identification of my ECM.
You have to understand the monitors are not cleared. They are there to tell you the car is operating correctly. They are set by driving the so called drive cycle. You are not deleted or clearing anything. Your build a driving data base the car uses to determine if the various systems are operating within allowable ranges.
If the car can't determine this then the monitor will remain in the unset condition until it can. Sometimes this can take a while too.
.
.
.
Does it matter if the TCM was in an XK8 or any other 4.0L Jag? I'm finding a few with the 003 extension but according to the sellers they came out of an XJ8. I've also found a place that repairs TCMs and ECMs but I don't know if that is what is needed. I'm going to see if I can call the local Jaguar dealer and ask if them if I bring the car to them, even though they do not "work" on cars "this old", do they have the equipment needed to determine what the extension is of the ECM that is in the car. I'm finding several ECMs out there with the correct first part of the VCATS but like mine most of them do not have the second label on them that show the second part.
Thank you for the info but I'm just going to leave it to the smog repair shop. I personally think it's all psycho babble and b/s. If "resetting" requires warming up every 2001 Jaguar XK8 for 3 minutes, then driving it 55 mph for 3 minutes (or 5 minutes depending on the "drive cycle" you read), then coasting down to 20 mph (or a stop) and then repeating these steps 2, or 3 or 4 or . . . times until the "monitor" resets, what is it "monitoring?" I'm sorry but it's just too frustrating to deal with a system that has no logical explanation as to why certain things are required before it can do it's job. Especially when those "certain things" have no definitive measurements, i.e. "sometimes this can take a while". If I want to reset a circuit breaker I move it to "off" then back to "on". If it does not stay there I know there is a short that I have to find, and that short is somewhere along the wires attached to that breaker. Once I find the short and fix it I go back and reset the breaker. Here, all I get is "keep driving the drive cycles more". That's like saying keep flipping the breaker back and forth and hoping the short goes away. How does driving the car in a pattern no normal person every drives in cause the system to "build a driving data base"?
