XK8 Gurus,
I am having a heck of a time solving my OBDII problem. I hope you can help.

I am troubleshooting the failure of my scan tools (Ancel BD200 and Innova 3100RS) to communicate with my 1997 XK8 (J26 engine). With either scanner plugged into the DLC (OBDII) port, the scanners say “cannot connect to the vehicle”. When trying to query specific modules I get the same “cannot connect” message.

I tested the DLC and ECU plug 10 with a multimeter and an oscilloscope. Can you help me interpret these results?

The CAN bus multimeter testing at the DLC (OBDII port) seems normal, I think:
With key off-
1. V on pin 6 to 14 is 0V.
2. V pin 4 to 5 is 0V.
3. R pin 6 to 14 is 61 ohms.
4. R pin 6 to 4 is 0 ohms.
5. R pin 16 to 4 is 0 ohms.

With key on:
6. V pin 4 to 5 is 0V.
7. V pin 6 (CAN hi) to pin 14 (CAN hi) is 0.3V.
8. V pin 6 to pin 4 is 2.95V.
9. V pin 6 to pin 5 is 2.95V.
10. V pin 14 to pin 4 is 2.64V.
11. V pin 14 to pin 5 is 2.64V.
12. Sum of steps 6 + 8 is 5.59V.

Oscilloscope on the CAN bus shows:
13. Scope on pin 6 (CAN hi) shows what looks like normal CAN signals.
14. Scope on pin 14 (CAN lo) shows what looks like normal CAN signals.

Multimeter testing on pin 7 (K-line) shows:
15. No continuity between DLC pin 7 and pin EM10-13 at the ECU.
16. No short to ground of DLC pin 7 and pin EM10-13 at the ECU.
17. No short to 12V of DLC pin 7 and pin EM10-13 at the ECU.

Oscilloscope on the K-line shows:
18. Scope on pin 7 shows 12V baseline when the engine is idling and the line is quiet.
19. Scope on pin 7 shows “query” signals when the scanner queries the network.
20. Scope on pin 7 shows no apparent response from the ECM or other modules.

Questions:
21. Is there an explanation for the “no connect” message and these test results?
22. Does seeing the query signals on pin 7 indicate that the wire is intact or would I see query signals on pin 7 even if the pin 7 wire is broken?
23. Failure to connect to any modules on the network makes me think there is a problem with the K-line from pin 7.
24. Is there any documentation or photos, that show the exact locations of CAN and K-line connections and splices?

Very big thanks.
DrDan

 

Rather Unusual, I haven't seen this one. If it may help, maybe inspecting continuity between the wire harness and the ECU is to be in order. If you didn't have the electrical guides already we do have them available for your specific model year XK8.

Also make sure you can devices are working them selves by connecting to other vehicles. There may be a sitation where a rodent could have broken a wire or maybe a wire rubbed on metal. There could also be a blown fuse, specifically I believe there's a fuse for the OBD in the driver side fascia box.

 

Looking at your test results, I have a few comments:-

 

dibbit,
Thanks for your response. I rechecked the resistance readings you questioned.

Resistance between pin 6 to 4 reads OL.
Resistance between pin 14 to 4 reads OL.

Regarding failure of my scanners to connect to the vehicle, I rechecked continuity between the DLC and ECM.

Rechecking, I do have continuity between DLC pin 7 and ECM pin 10-13 (K-line).
The pin and socket at the ECM for pin 10-13 look good.
Rechecking, I have continuity between DLC pin 15 and ECM pin 10-12 (L-line). The pin and socket look good.
Using the oscilloscope on DLC pin 7, I see what I think are scanner blips because pin 7 blips are simultaneous with messages on the scanner. I do not see any response blips. And both scanners indicate no connection with vehicle, although both scanners previously connected to the vehicle.

Does this indicate that failure of the scanner to connect to the vehicle is likely due to a faulty ECM?

Are there other confirmatory tests that I should do?

Again, thanks for your help.
Dr. Dan

 

Standard OBDII proper is only offered on serial/ISO-9141. From what you are saying, the scanner is not able to connect. Is your scanner Jaguar/Land Rover aware? If so, can you get diagnostic from modules on CAN or SCP? It will not be OBDII, but may help narrow down the problem.

FWIW, I seem to recall there is some form of network protocol bridge built into the instrument cluster. Another thing to investigate I suppose.

Best of luck, keep us posted.

 

That is the correct reading - OL means "over limit" in other words a resistance too high to measure. I don't know why they use something so easily confused with 0, which is the complete opposite.

As fmertz has pointed out, there are other networks on the car you can try connecting to. Pin 7 is the ISO9141 network for standard PIDs. I don't know if your scanners have the ability to connect to individual modules such as the ABS to see if you can get anything to work, but it would be worth trying.

Your vintage of ECM is prone to failure as the electrolytic capacitors start to fail, so that is a possibilty. You can open the ECM up and inspect it for any evidence of leaking caps or send it off somewhere to be tested/repaired. This is also a straightforward DIY job if you have the soldering skills.

 

fmertz and dibbit,
Thanks for the suggestions.

Re ECM, I opened the unit and inspected the boards with a magnifying glass. The capacitors look OK- no apparent leakage or bulging.

Re CAN network, I put an oscilloscope on CAN hi and CAN lo. I observed signals that look similar to those I see on YouTube except that the wave forms look "dirty". Can hi and CAN lo generally mirror each other but the signal is "jagged", perhaps due to artifact or my not tuning the oscilloscope properly. The voltages on CAN hi and CAN lo are roughly what I expected, although the amplitude of CAN lo signals are not as high as CAN hi. I am a novice at using the oscilloscope.

I cannot get a response on my scanner to any other modules. Does the ECM need to send a "wakeup" message to the other modules to tell them to respond to the scanner query?

I am inclined to think that I have a bad ECM. What do you think?

Thanks,
DrDan

 

Is the car itself running ok - i.e. you can unlock the doors, start the engine, see the RPM on the instrument pack, open the boot with the dashboard button, the gearshift surround shows what gear you are in as you move the lever? All those things indicate the different networks are connected and working. What actual faults do you have on the car (if any)?

 

See this thread:
https://www.jaguarforums.com/forum/x...1/#post2779634

 

Thanks. Maybe the OP can confirm if this is still an intermittent problem or the scanner will now never connect.

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I had this problem on my 06 STR. Turned out the obd2 connector pins had been splayed open from prior connections so the puns werent making good contact. I had to replace the connector body as well because it was slightly damaged. I got new pins and plastic connect body from digikey or place like that. I believe I made a post about it in the s type forum. I dont have my receipt folder close by or id give u the part numbers. I can post the later when im at the shop. Anyways those pins seem kinda weak. But I got the right crimper and swapped in new pins into the new connector body and it solved my no connection problem

btw I could probe the pins and get good readings but when I bought a breakout box for obd2 itd show no signal. So dony rely on just probing with a neter lead bc it will fake u out

 

Thanks to fmertz, dibbitt, and aarcuda.

All of the car functions work (remote lock/unlock/boot opening, engine start, instrument pack, gauges, gas and boot button on dash, gear shift surround lights, etc) except for recurrent failure of scanner (both Ancel and Innova) to connect to the vehicle. My oscilloscope shows what I think are normal CAN hi and CAN lo signals, normal query signals on pin 7 (K-line) but no response from the ECM on pin 7 (K-line). Recall from above that I have good connectivity from pins 7 and 15 to the ECM connector 10.

In July the scanner would occasionally connect but since the end of July the scanner has not been able to connect. In July I started getting "lumpy engine" about 1 minute after start up. Engine ran perfectly for about 1 minute. The last DTC codes I got from the scanner in July were :
P0333 (knock sensor bank 2)
P0352, P0353, P0355, P0358 from GroupB cylinders
P1368 ignition control module bank 2
P0405 EGR
P1000

My scanners try to read ISO9141, KW2000, PWM, J1850, VPW, and CAN but cannot connect.

I am thinking I may have two problems: 1. Failing ignition control module 2, giving the P035X codes and lumpy engine, and 2) failure of the ECM to answer DLC queries on pin & (K-line).

What do you think?

Thanks,
DrDan

 

WhiteXKR mentioned 10 years ago that on early cars the L line and the K line need to be connected to wake up the ECM:-

https://www.jaguarforums.com/forum/x...ooting-144485/

Given that you used to be able to get your reader to connect, this may not be your problem, but perhaps worth trying. I would perhaps also double check that pins 7 and 15 on the DLC are in fact connected all the way through to the ECM. You could also put your scope on the connections at the ECM end and see if your scanner is in fact getting that far. If it is physically connected and the lines aren't shorted, then all that is left is the ECM itself.