I suspect that my ECM has gone bad. I just wanted to know if it is possible to just swap it with a used one purchased online. Will I have to get the dealership to do anything or is it a simple part swap. I plan on buying the same type I have and one that is for my VIN.
Thanks
Brad

 

I believe several car modules will need recoding if you change the PCM (ECM) and car will not start until they are. You may also have problems with the mileage displayed - a tech may comment if you're lucky, but basically don't do it without at least arranging with dealer first.

It would be far too easy to steal cars if this was plugnplay.

BTW, it's more likely the wiring than the PCM.

 

Do you have a PTEC (PowerTrain Electronic Control) or an ECM???? (PTEC=2000 - 2002) Early S-Types do not have a CAN buss and the 2003 > have separate ECM/TCM and a CAN buss. You might get more of an answer if you provide info about your car. The 2 types of S-Types are VERY DIFFERENT.

Some modules can be swapped and reconfigured, but some CANNOT and must be programmed from the factory and shipped the the dealer and be configured to your car.

bob gauff

 

I have been fighting this problem for some time now. the faults I receive are all CAN related. I have checked the entire CAN bus and it is good. I noticed today when entering "Engineering Test Mode" on the instrument cluster that the PCM displays on "--". From my research on the forums people say that means it isn't communicating with the IC. I know for a fact that the CAN bus is good between the ECM and the IC. This is why I believe the the problem is the ECM.

Thanks
Brad

 

Does the car start?

Does it drive?

If it does, the CAN must be working, I'd think!

Bob is right, you really need to put your car details in your profile otherwise you risk getting a wrong answer.

BTW, there are multiple types of S-Types with CAN yet different PCMs. (Back to putting the car details in ..... yes, your profile!)

 

I have posted a thread about this issue a few months ago. https://www.jaguarforums.com/forum/s...ad.php?t=37894

I have an 05 S-type V6 auto with 48000 miles. This is an intermittent problem I have been having. The car will not crank. Nothing happens exept for alot of faults. When the problem is occuring I receive the following faults: Transmission fault, ABS fault, DSC unavailible, and parkbrake fault. When the fault is occuring the OBDII reader can't connect to the vehicle either. Once it decides to start working, everything works perfectly and the only fault I can pull i P1797 CAN TCM/ECM network malfunction. I have thourghly checked the CAN network and it is good.

 

It sounds very likely to be a wiring-related problem, probably one of the ones that crop up here occasionally.

Have you cleaned and reconnected the main vehicle grounds? Also, power?

Have you checked for any problems with the wiring harness(es) that are behind the front bumper and up inside the wheel arches (wells)?

Another possible would be damp in the PCM whether its wiring or actually inside - but you'd need to have water getting to it. It's not common.

You might consider getting AutoEnginuity because it can connect to the car's modules across each of: CAN, J1850 PWM & ISO 9141. Then you could see how many / which modules vanish when the trouble occurs. You'd need the jag-specific AE so about $450.

I'm guessing it happens rarely enough that you feel by the time a dealer looks at it the fault will be absent - but is that the case or if not then why not a dealer / competent tech?

 

A quick note: an ordinary OBD tool connects using ISO 9141, not CAN.

 

The nearest dealer is to me is about 80 miles away and when the problem is occurring "which is more often than not now" the vehicle can't start. It has been about 2 weeks since the car has started and I am trying to avoid towing it that far to a dealer. I'm sure I can just bring it to the dealer and have them fix it, but I called them and they said they would just throw parts at it and I'm trying to save money. I know that the OBD reader doesn't communicate via the CAN bus, I was just adding that in for more information.

Once it gave me a bunch of other errors and they were all CAN etc. I have already removed all modules connectors and cleaned all connectors. I have even spliced into the bus to allow me to bypass the existing disconnects. I've cleaned the grounds and replaced the battery.

I have noticed that the J-gate also doesn't receive the brake on/off signal while the fault is occurring. You suggested checking the wires in the front of the car. What wires are you referring to? What type of signal goes trough these wires? I was the electrical schematic shows that the CAN HI/Lo wires meet in the ECM and IC. Everything I find online says P1797 usually is open or a short in the bus, but I have checked it out.

You said to check grounds and power. What modules could cause all the faults that I have.

Thanks again
Brad


P.S. The tech at the dealer told me he never heard of something like this and that they would just throw parts at it. He said that he thinks it would wind up costing way too much and he actually told me that he wouldn't bring it in if he was me.

 

A smallish number of people have posted (here and the .co.uk forum, but it also hit Evo's test STR) about corrosion in wiring that runs where I indicated.

You'll need to search but here are a couple:
http://www.jaguarforum.co.uk/viewtop...wiring#p156669
http://www.evo.co.uk/carreviews/evol...e_42_v8_r.html

The main clues were weird, sometimes meaningless/confusing codes. As the damaged wires seem to vary a bit you can get almost any symptoms.

People have had trouble with the SCLM (steering column lock module) and as you know with the J-gate. I can't imagine diagnosing them without something like AE.

If you really knew for certain it was a CAN-only issue I reckon you could find it but you'd need something to talk to the CAN modules and then (say) remove them and re-add them to home in on the fault. You might do it with a DSO (but don't even think about it if you don't know what that is) but I think something like AE is your best bet.

I don't think you do know for certain that it's CAN-only. (But it could be.)

Some of the modules appear to have 2 CAN connections judging by the diagrams etc but I don't know exactly or certainly why (it's not like I designed it!). Either they're just for convenience or they're some sort of CAN repeater (which would be electronics).

You probably know the ICM (cluster) is unique in that it is a "gateway" which I reckon means it copies some data packets from bus to bus. I bet it only copies certain packets so as to keep traffic down.

Although it stops you using the car, an all-the-time fault gives you a far better chance to find and fix it.

 

I'll check those links out and look for those problems on my car. Thanks for the advice.

Brad

 

If you decide to examine the harness wires there are posts about it here & the .co.uk forum. Here, about how to remove the bumper and there about stripping off the covering etc. Not particularly easy or quick

 

You wouldn't happen to have the 2005 stype electrical guide whould you?
I am using an older one that isn't quite the same as my 05. It is mostly the same but there are a few places that the car is pinned differently.

Thanks
brad

 

I believe it's on jag's GTR / TOPIx which you used to be able to join for as little as 1 day and download what you needed (I've not needed it recently so don't know if it's still like that). It was quite cheap to do that.

 

I once had an electrical problem on a 4-stroke, 4-cylinder motorbike that was traced to a fractured solder joint. Erratic behaviour, inconsistent, sometimes worked perfectly, other times it would stop or not start, and it got worse with time. It was a bad solder joint inside the ignition module (bike is carburetted). Maybe open the ECU and check for bad solders? I don`t know if it is feasible in the S-Type, just trying to help...

DF

 

It's very expensive if taking it apart damages the PCM. Be VERY careful.

 

Well I examined the wiring harness that runs behind the front bumper and it was fine. There wasn't any corrosion that I could find or see under the insulation. I visit the Jaguar Topix website and purchased a membership. This is a very good site with a lot of information. I found in the workshop manual section, the troubleshooting tree for my DTC code P1797. I followed the tree and it says to change my ECU.

So I guess that will be my next move. Since you guys say that it isn't something I can do, I will contact a dealer and see what my options are. I was hoping for a wiring issues, so I could have avoided the towing bill and dealership cost.

Thanks for the help
Brad

 

Probably worth calling more than one dealer to see who's cheapest. Could be a scary price, though

 

The V6 cars are pretty common so I would search EBay and junk yards for a used PCM. Since you have done this much troubleshooting I think you could change the PCM yourself!! It’s actually very simple if you can get the old one out!! Sometimes they get really stuck in that rubber collar. The picture I posted shows the two long threaded studs but it does not show the rubber collar that traps and isolates the PCM when it’s mounted thru the firewall. These two long studs extend thru the rubber and when you tighten the nuts down it squeezes the rubber collar tightly around the PCM. Remember the electrical plug faces towards the front of the car.

Please buy the JTIS off EBay its only $10 with shipping and it is well worth it. Even if you get a subscription to the GTR!

One dumb question (It's from experience and not trying to tell you what to do!). Are you positive that the battery is good and the connections are clean and tight??
.
.
.

 

I am almost sure that if you plug in a different (but same year) PCM it will talk to the other modules. Among other things it will exchange and compare security data and then as it won't match it will immobilise the car and go into anti-theft mode.

Maybe a tech will know and post details but I can also imagine they may be unable to do that for professional reasons even if they know.

The PCM may also adopt the higher of the two mileages that may be present - if jag PCMs store the mileage.