Hi Guys

Just brought my XK8 out of winter hibernation and preparing for the annual inspection. ODB11 Data link cannot communicate on the CAN system. Some SCP faults do register but nothing on OBD11 network.

Battery is fully charged and have checked both fuses that relate to the DLC.

On to the step by step fault checking - have permanent power to the DLC on Pin 16 and have ignition supply on Pin 9 with the ignition on. However, the next test fails - Ignition Switch ground. Pin 1 to ground should register 5 Ohms or less - mine registers 14 MegaOhms. Guide says check the high resistance circuit - refer to circuit diagrams. At this point I am lost!

Are there any techs out there that can advice me on my next steps - do I have a short circuit somewhere or a grounding fault - if so - where might the problem be?

Cannot get the car tested without working ODB11 - all tests in vermont now link computer at testing station with DMV - so no leeway from the tester.

Thanks in anticipation of suggestions.

Regards

Gareth

 

Could be high resistance or open circuit. I'll have a look on the wiring diagram and get back to you.

 

Im assuming by pin 1 you mean pin 1 on the connector going into the ignition switch, red and white wire? The ground for this should be in the driver side kick panel, check this ground point and make sure there is no broken wires, loose connection, corrosion.


Did you check the resistance of that wire with the connector @ the BCM disconnected? You might be measuring internal resistance of the BCM as well if that's the case.

 

Hi JBzXJ40
Thanks for the reply. First of all my drivers side may not be your drivers side as I see you might be from NZ or are you now in Houston? I am talking about Pin 1 on the DLC which does go to the ignition (ii) position. However, my diagram shows the wire to White/Orange.

I have to confess electrics is not my strong point - and Jags Diagrams aren't particularly easy for a novice to follow - but it looks like the Ground point is FC38L.

I'll try and find that in the JTIS electrical section - I know the locations are in there somewhere. But I'll try the kick panel first. Can you explain a little further about the BCM possibility - at the moment that comment went straight over my head!

Kind regards
Gareth

 

R/W wire to ignition switch is only grounded at position iii (crank), otherwise will read internal resistance of BPM.

Black wire to ignition switch is grounded at FC38, the same place as the DLC.

W/O & W/N wires to DLC should read low resistance to ground with ignition switch at position ii.

I imagine that if there was a problem with the switch or its grounding that you'd also have a raft of other issues.

No disrespect, but are you sure that the diagnostic tool is working properly? Otherwise - long shot - CAN connections to the DLC appear to come direct from the Major Instrument Pack on yellow and green wires.
There are two connectors at the bottom of the pack that can be seen once the veneer panel is removed. Wouldn't hurt to remove & re-seat these. Make sure that the battery is disconnected first.


NB:JTIS bears the following warning for early cars (my emphasis):

† NOTE: Early production vehicles (up to VIN 003300) have connector pin
numbers that differ from the volume production pin numbers shown.
Use the wire color code for pin identification on early production vehicles.

HTH,
Mike

 

I am currently living in NZ now, but I am originally from Houston.


As michaelh said, you'd probably have a bit more not working if it was a faulty ground, as that ground is for multiple things.


As for the BCM comment I mentioned, if you are only measuring resistance from one end ( at the DLC ), you need to see where the other end of that wire goes. If it's going into a module, then you will be reading the internal resistance of the module as well, when you need to isolate the circuit by disconnecting at both ends and checking resistance of that wire only. Not a good idea to be measuring resistance of a module.


Do you have anything else on the vehicle that isn't working properly?

 

Hi JBzXJ40 and Michael

Thanks for your replies. Have done a lot of work on this since we last connected. Have traced all the CAN connections (G and Y wires) from termination at the ABS module through all CAN connected modules - ABS, TCM,ECM,Gear Selector,MIP and finally DLC. All show good continuity. Have now printed off the JTIS about 16 pages of checks for Ground checks - which I may work my way through - depending on answers to below.

I have no other faults showing on dash - no warning lights, no check engine, etc. I have three CAN readers - two OBD2 and one specifically for Jags. The 2 standard readers won't connect at all. The Jag reader does read parts of the system - it picks up several inconsequential faults on the SCP network - seats and steering column out of range and the like, but the OBD2 diagnostic section fails to communicate. It's all very weird!

I have seen the early model warning Mike and mine is later. I also saw a weird warning that there are two logic grounds coming from the steering column that must be kept separate - haven't moved any ground so assume that is irrelevant.

Does anyone know if a Jag Dealer with their diagnostic system would be able to track this fault much more quickly - I had a terrible couple of weeks 2 years ago trying to get an airbag light to stay off. Tried everything. Eventually took it to a dealer who diagnosed a blown fuse 2 minutes after connecting it to their computer. I fuse I had checked and thought was OK! I don't mind paying a couple hundred bucks if it solves the problem fast. Can't use car until this problem sorted.

Thanks for your input guys.

Gareth

 

Still somewhat confused by the 'Ignition Switch ground...'. The only ignition switch connection that is unconditionally grounded is the black wire, which is pin FC4-5. Pin FC4-1 is a signal to the BPM in key 'crank' position (the Red/white wire).

Is this step-by-step from a document, or being suggested by your diagnostic tool? It may well be throwing you off track, or JTIS is wrong...

Are DLC pins 1 & 8 at ground with the ignition switch in position ii?

One check you can make:- the CAN should be terminated at each end with a 120 ohm resistor, so you should see 60 ohms if you measure across the yellow and green wires (pins 6 & 14 at the DLC will work), but if the CAN really is compromised I'd expect other (possibly drivetrain?) problems.

I know you can't use the car atm but can you drive it at all to see if you have any issues?

I don't know how smart the dealer diagnostics are so couldn't say either way, but if you're contemplating that route I'd want a 'no diagnosis no fee' deal:- his kit might have the same communication issue.

Mike

 

Hi Mike
The documents I am working from are the fault diagnosis sheets from the JTIS.
An interesting development. My reader is a Carsoft i930 which has been pre-programmed for Jaguar/Landrover cars. Selected the 97 XK8 setup. This time - went to the diagnose section of the reader and selected Read ECM - reported NO DTCs. Went on to Read Data Streams and chose a wide range of sensors to display 'Live' data. out of about 16 different sensors - all sensors displayed live data.


Went back to the OBD2 section and again failed to communicate. Also then checked can the reader read the codes in the TCM and MIC - again responded 'no DTCs'. Live streams from these modules also worked. Beginning to think that maybe the OBD2 function of this reader is for NON-Jaguar/Landrover cars - as I have used this reader to read OBD2 on my Ford Expedition with no issues.


I get no error messages or lights on the dash - and the engine runs sweet - but have not driven the car since last Autumn when the car was laid up for the winter. Did do a front end rebuild over the winter - All Tensioners and chains. But must re-iterate - car runs sweet.


I think I'm going put everything back together and just take it to a testing station and see if their computer links correctly. If not, I'll talk to my nearest Jag Main Dealer (160 miles away in Hartford CT) and ask what they might be able to do. Good idea to try and negotiate and no fix no pay deal.


Thanks for your continued help.


Gareth

 

My confusion sorted. I've looked at the JTIS step-by-step, and test #3 is Ignition switched ground
That's saying check pin 1 (white/orange wire) at the DLC should read <5 ohms to ground with the ignition switch at position ii (on).

The next check is pin 8 (white/brown wire) at the DLC should read <5 ohms to ground with the ignition switch at position i (accessory).

If your reading is very high in the first check then you have open circuit between the DLC and the ignition switch somewhere.

Both of those wires only appear to pass through one junction on their way to the ignition switch: FCS20 for the white/brown and FCS26 for the white/orange, so they should be fairly easy to trace (but it is a Jag...) Given that there's a bunch of other circuits grounded through FCS26 I'd guess the o/c is between there and the DLC, or maybe the DLC socket itself.

Mike

 

When reading the ohms he was getting the first time, sounds like an open circuit. But if you're checking resistance with the module still connected, most likely you'll be checking the internal resistance of that circuit inside the module as well, you wont get the correct reading. Should isolate the circuit when checking resistance.


Verify the resistance of the wire between the DLC and the ignition switch, and report back. When checking for DTC's, do any modules come up as communication error?

 

Hi Mike and JBzXJ40
Thanks. I will check those links tomorrow - for the record and future readers of this thread - FC20 and FC28 harness connectors mentioned in Mikes post, are in fact FCS20 and FCS28. These links can be seen in Fig. 02.1 in the XK8 Electrical PDF. If anyone else is following this and wondering what we are talking about - if you have access to the JTIS - the fault finding checklists for tracing faults in the Communications Networks is section 418-00. We are closing in!


Thanks again

 

Hi There
why not take your car to a local Auto Zone or Advanced Auto in the area and let them try to read the codes, I had an issue a couple of years ago and my local indis reader would not connect to my 2001 xk8. I went to Auto zone and they used theirs worked ok so I bought one $100 but best investment I ever made.
Just a thought

 

Thanks for the post Jeremy
I have three readers that have all worked with the XK8 in the past - the i930 reader is specifically for Jags and it does read the SCP network and it will connect to all the live streams on the CAN network - it just won't read the OBD2 fault codes. While it might be worth a try if the car were on the road, it is unlikely that all three readers would go wrong at the same time - much more likely to be a wiring fault. Trouble is - where?!
Thanks again.
Gareth

 

Hi Guys
Just to say job is on hold for a couple of days while I get a new, better! Multi-meter and some professional test probes. I am getting very erratic readings when I perform the various ground fault tests detailed in the checklist - sometimes pass, sometimes fail. Either faulty multi-meter or maybe faulty DLC. Just for the record, it seems that Jaguar made removal of the DLC impossible without removing the entire fascia. Cannot get to the nut the holds the drivers side fuse panel in place (that would enable the DLC to be removed) - without taking the fascia off! Ridiculous!
Will continue once new gear arrives.
Gareth

 

I don't know if you mean this sentence literally, but on our cars (my car for sure), the government mandated, standard OBDII is only available over the older ISO-9141 protocol. I am talking about the run-of-the-mill check-engine light, fuel trims, emission codes, etc. Other proprietary Jaguar-specific diagnostics and communications are available over CAN, SCP and ISO-9141, but OBDII proper is only ISO-9141. As per Wikipedia, it is pin 7 and pin 15 of the diagnostics connector...

 

hmm... the 930 is known not to work with some of the modules in some of the cars so maybe the car is fine but not the 930.

 

Also, the OBD pinout shows pin 1 (and pin 8) of the DLC is 'Vendor specific', so a generic reader wouldn't know what to expect and likely won't have a connection to that pin?
So a problem with the switched grounds might only affect the Jag-specific reader.

The grounding needs to be fixed, but not sure it's the cause of your issue.