Today I was out doing errands. I stopped for about 5 mins and then started car normally. It would not come out of park. Showed transmission fault and no DSC. Restarted several times and finally came out of park. as I drove off, I got the service engine yellow light and a reduced performance message. I stopped and scanned the code with my scanner and showed a P1642. I cleared the code and the light and message disappeared. It did not reappear during the ride. I also got a transmission fault a few days ago. It did not show a code and disappeared when I shut down and restarted. The trans also does not seem to shifting as smoothly as it usually does. Especially as the transmission downshifts when slowing to a stop.

Ideas? Is a fluid change in my future. 57,000 miles
2004 XJ8 VDP.

 

Anyone?

 

That code is for a communications network fault. The book says it is either a short in the CAN or a bad tranny module. The test condition for it is ignition on with engine off for 30 seconds. If it is an intermittent fault, you may be able to drive it by shutting it off and then meeting the test conditions.

This fault does NOT account for the inability to shift out of park...but the manual says to check for other codes. It mearly results in reduced performance.

Sorry, but I don't know any more than that...the one time I got a com network error with my car was when I had the real data mode running on my scanner. It was spurious, though.

 

Thanks for that. It sounds like a spurious fault. That code will cause restricted performance. I hope it is not the tranny module.

 

How old is your battery?

 

New... 4 months.

 

Well it happened again today! When I started the car after my second start I immediately got a parking brake fault, transmission fault, CEL, and reduced performance. Scanned and got the same P1642. I cleared it, restarted and all was well. Had one more stop and started without incident. I tried the ignition on for 30 secs and got no messages.

I am now gun shy with the car. If I had not had the scanner I would have been forced to drive 25 miles home with reduced performance.

If it continues I will take it to an Indy shop I know of that has the Jag diagnostic setup. No dealerships for me.

 

P1642 = Can short circuit fault; Control module failure - check for additional flagged DTC(s) to locate control module source.

If it's not a bad battery, then i'm not sure where to start, I know from experience when you reflash a transmission with the park brake on, you have to re-calibrate the park brake afterwards. They are kind of related.

There must be more codes. Without more info we are shooting in the dark.

Try parking the car with the handbrake off (hold down the button with foot on the brake when removing the key).

 

Anything recently happened in relation to the car ? Been through any deep puddles or similar ? I had the CEL light failing to go out when I started the car. My recent work had been tranny fluid and filter change. Shop disconnected some plug connections, cleaned and checked the contacts, and all well since.

 

My scanner showed no other codes. I am taking it tomorrow to a shop that has the equipment to talk to this beast. I will let you know what I find.

What will parking with parking brake off accomplish?

 

If there is a problem with the parking brake module, this should stop it from kicking up a fuss; if you don't use the park brake, no park brake fault on the dash?

 

Is there a locking pawl in park? Dont want it to roll away. the parking brale thing does not bother me nearly as mich as the trans fault. No puddles. Rarely driven in rain. Only did the "won't come out of park" once.

 

Yes it locks up when in park.

The idea of not using the park brake is to try & isolate the problem.

If parking the car with the parkbrake off stops the code / restricted performance from coming up, then it points towards the park brake module being the problem.

And TBH i've read more posts on this forum about the parking brake playing up than a transmission control module....

 

It would be worth checking and cleaning the gearbox connector plug.

 

This is the series of messages that usually indicates a failing Throttle Body. The TPS may be going bad, and it generates all these messages in the process.

 

Thanks!

 

What is the code for a bad throttle body. Why wouldn't it throw that code instead of parking brake and transmission?

 

My throttle body had a bad position sensor, that progressively got worse. The dash indications were exactly what you are seeing on yours, and the engine went to high idle limp home mode...but it did give the TPS disagreement code (I forget the exact code P11xx or something like that).

I don't know why, but these cars throw the parking fault into a lot of seamingly unrelated failures.

The code you are getting is a com code, so some ecu's are obviously not in touch with the rest of the system. Hopefully the Jag diagnostics equipment can tell wich ecu's are not communicating. From there it would be a matter of checking connections, or replacing the errant ecu.

 

It hasn't done it the last few times I have driven the car. I can clear the fault easily and will wait till I get something concrete. I don't like chasing spurious faults.

 

Try cleaning the TPS connector plug. If the problem is there, sometimes a cleaning will give some additional time. The sporadic nature of this failure is normal. What is happening is that the carbon track inside the TPS is damaged from wear. It will gradually get worse, so replacement becomes necessary.