Hey guys,

I've had my car about 6mos now and put 10k miles on it. 2000 XJR, 100k miles now. I did the timing chain job right after I got it.

As long as I have owned it, it has idled rough, and the symptom can be intermittent. And if I let it idle to long, it goes into restricted performance.

I was never able to get any meaningful codes from it other than random cylinder misfires. I had gotten cylinder misfire codes on up to 6 different cylinders. The car still runs very strong otherwise(14.07 at 101mph). So I'm pretty sure the coils are OK. I believe that I was only getting cylinder misfire due to it being in RP and then trying to go over 1/3 throttle?

More recently the car has been going into fail safe engine mode. Now I am getting P1316, and P1121. I tried unplugging and replugging in my throttle body. The problem persists. It is much worse on cool moist mornings.

My research here indicates that my TPS is likely bad and that my TB needs to get rebuilt. I was just hoping for a little confirmation before I pull the TB and send it to ASI!

Anyone care to chime in? Is the TB issue likely creating the idle and misfire problem?

Thank you,

Keith

 

Brand new battery?

 

Tested OK at 12.7 volts.

I really hoped it was a weak battery. I also get the ASC/TC all the time and the coolant level low light intermittently.

Should I do the battery first anyways?

 

I don't think asc/tc and low coolant light are related to your throttle body issue. I'm not sure about the battery situation, do you know how old the battery is?

as far as the failsafe mode and the p1121, my car used to exhibit those, a new throttle body was the solution in my case

good luck

 

Yes. A battery can show a float charge that looks ok but has no load capacity.

Also clean the MAF, fresh air filter, and clean the connectors on the throttle body.

 

I took my TB off tonight and tested it. Tested the TPS for resistance while forcing the throttle blade by hand. Left two leads showed normal change in resistance with no dead spots. Right two leads also tested OK.

Then I tested the the connector on the throttle cable side. Left two leads seemed OK. Right two leads only showed a marginal increase in resistance, then it declined as I rotated the thottle cable wheel. Note, I was rotating the throttle wheel on this side instead of forcing the throttle blade like I did to test the TPS.

Is this normal behaviour? Or are those two right leads on the throttle cable input side not functioning normally? Did I even test the thing right? Do the motors that drive the blade go bad?

Any input is greatly appreciated.

 

They could all be sensor issues. I was hoping to find low battery voltage and explain all of the problems.

 

If you don't know how old the battery is I would start by changing it out. I am amazed at how sensitive these cars are to weak batteries.

If you still have problems send the TB to ASI.

Dave Christensen
65 Etype OTS
69 Etype OTS
03 XJR

 

New battery. Rebuilt TB from ASI with what looks like a new TPS.

It still idles rough. After extended idling, it throws the Restricted Performance warning. And eventually it also went into Failsafe engine mode.

Codes:

P0300
P0307
P0308
P1316
P1121
P1642
P1000

I am unfamiliar with P1642, I don't think I've ever seen that one.

 

It's one of the less informative of DTC's -

P1642 : CAN circuit malfunction

Possible Causes
1. CAN short circuit fault
2. control module failure - check for additional DTC's to locate module source

None of your other codes are indicating a specific module.

Graham

 

I had the P1121 code along with many others read this and see if it fits.

Link JagRepair.com - Jaguar Repair Information Resource

 

All he did was replace the brake switch and get the TB rebuilt. Could it be the brake switch?

At this point I'm ready to drop it off at a shop and let them diagnose it. I was really trying to avoid that though. There are so many issues I suspect now but I don't just want to keep throwing parts and money at it.

1. Egr valve?
2. Lambda sensor?
3. Cam position sensors?
4. Crank position sensor?
5. Fuel filter?
6. Clogged/bad injectors?
7. Multiple bad coils?
8. MAF sensor?
9. Vacuum leaks?

Ugh, those adds for new jags are looking more and more tempting.

 

Let's see, it sounds like you're a bit over faced with potential work, no problems,

the first 3 codes are random misfires...
P01121 is the TPS...(rather odd after a rebuild)
P1642 - ECM fault, failsafe mode - limits revs to 3000rpm etc.

I think the TB is causing issues and flagging the 1121 and 1642, if you've limited control over the TB it's likely causing the misfires.

An electronic error ,say 'out of range signal' to and from the TPS on the throttle will cause a CAN error logically.

ECM senses this and inhibits the engine.

Give the connectors on the TB a re-seat, disconnect/reconnect. Then perform a hard reset. Do this by disconnecting the neg lead and hold it to the pos post on the battery for 5-10 seconds to clear the ECM memory. connect the neg lead back up and start the car, let it re-calibrate the throttle and let it idle for 10 minutes to store the new TB values.
It might just be a bad connection. The above process should take less than 20 minutes.

The brake pedal switch is different symptoms. (Car cuts out coming off cruise)

 

As for the brake switch it was changed because no codes were visible once I got the P1121 I knew that the TB was the problem and I had it rebuilt. The link below is for your codes.

Your car is a MY 2000 and it had issues with the TB

Link http://jagrepair.com/images/TSB/310-06am3.pdf
You may want to see if your car falls into this using your Vin# Link http://jagrepair.com/images/TSB/XJ/S...ion%20S514.pdf

Link http://jagrepair.com/images/AutoRepa...7_ECM_2000.pdf

 

After installing the rebuilt TB then getting errors again, I did the ECM reset via the battery and the problem persisted.

 

It appears that I that I did overlook the fact you already rebuilt the TB sorry. If I recall correctly I think you may have a procedure to the car to relearn the TB. I did not need to do that. I recently had reason to call ASI about another problem and they were very helpful and appeared to be knowledgeable and aided me to success. I would suggest calling them it is possible the rebuild may be incorrect.

 

It does sound as if your new TPS is duff.
Nothing to lose by retraining the throttle as Gus suggests
https://www.jaguarforums.com/forum/x...connect-74146/

There's a thread here
https://www.jaguarforums.com/forum/x...acement-77560/
giving the resistance values for the TPS if you want to double check them

 

Any identifying numbers or markings on that "new" TPS?

 

Got the cam timing reset at a shop for ~2000 plus a couple other random things. Took care of the idle misfire. No problems for months.

Then P1121 came back today (rained very hard). Is it just my connector?

 

I just got 'engine failsafe mode' starts ok. was running ok. started making a rubbing noise on the underside on the passenger side - don't even know what that is....2000 XJ VDP 120K. any suggestions, info?