I have posted this problem earlier, but only as a mechanical problem, and maybe it's an electrical problem, so consider this is an official challenge for you great Jaguar forum electrical folk to see if I am barking up the right tree:

1999 XK8 constantly throwing out a P1384 code about a week after having the head gaskets replaced.

*I checked the wires and cleaned the connections to each VVT solenoid...no-go.
*I purchased a good used VVT solenoid, and tried both banks separately...no-go.
*I took the advice from several other threads on this site and several other sites as well, and I changed the oil from 10-40 to 20-50 and used a different brand of oil filter...no-go.

Here's what makes me think I may have a ECU problem:

The check engine light never came on during the first start-up and drive after trying each above step and clearing the codes each time...it only came on during the second start-up and drive, and not only that...the check engine light always comes on about 30 seconds into the second start-up and drive.

Does anybody think that this might be a coincidence? Sure seems strange to me after witnessing it 6 times in a row now.

Do ECU's do quirky things like this?

If I replace the ECU (several on Ebay right now), does it need to be 'flashed' or anything special, or is it a plug-and-play scenario?

I really appreciate any ideas out there!

 

It will have to be synced to the other CANetwork modules and poses a number of other issues like not having a stored VIN that matches the car. That takes the dealer level diagnostic system and enough knowledge to make it work.

Have you pulled the ECM and cleaned those connectors?

(disconnect the battery first!)

 

Those events sound like a normal ECM reaction to me. The check engine is often not displayed until an error has been repeated for a couple of test cycles. If you erase it the error has to be accumulated again.
If you do think it's the ECU, don't just buy another one, send it to a repair facility like ASI. They will test your ECU and repair if needed, no reflash required. Mine was faulty and works like new, also has warranty now.

 

P1384 activates the CHECK ENGINE MIL if it occurs during 2 consecutive “trips”. What you are seeing repeatedly is the designed behaviour because the cause has not been rectified.

The possible causes of P1384 are:

1. VVT solenoid valve to ECM PWM drive circuit fault
2. VVT solenoid valve to ECM ground circuit fault
3. VVT solenoid failure
4. VVT oil flow fault
5. VVT / camshaft mechanical failure

The VVT or harness connections disturbed during the head gasket replacement have to be more suspect than the ECM suddenly developing a fault. Almost too much of a coincidence.

Graham

 

I agree, its doubtful that the ECM failed right after the headgasket was replaced. I would revisit the tasks for the gasket replacement related to the VVT system. The hardest to find would be low VVT oil pressure due to wrong headgaskets blocking oil flow through the head. I have seen mor ethan one incorrect headgasket cause a problem like this. Assembly of the VVT units or damage to them or th ewiring harness during R&R of the cams could also be the fault. Just look at each item separately.

 

That's good to hear, as I really don't want to have to mess with the headaches nor the costs of repairing or replacing the ECM.

It started throwing the codes about 3 days after the head gasket repair was done.

What I also think is a bit strange is that right after I changed the oil yesterday, for the full day of driving with multiple start & drives, it didn't throw any codes at all.

Next day, it started all over again.

Pretty frustrating!

My mechanic agreed to borrow a scanner that is Jaguar compatible, and he will try to narrow it down...I remember he said that he had a difficult time finding out exactly how the timing should be set when he put it back together, so hopefully it's as simple as the timing being off a couple of degrees.

I'll cross my fingers and keep you all posted.

Thanks to all for your help and support.

 

It's not the # of starts & drives. It has to heat up by quite a large amount, so must start off cold. (You can read jag tech docs for more info, e.g. codes PDF.)

A small number of codes need an overnight sit.