Hi. My Jag went onto 'failsafe' mode yesterday so I pulled over. Turned it off, waited, turned it back on and continued. This is something that happens every two months or so and it usually clears after one turn off/turn on. However this time it did it again about 10 minutes later AND the check engine light came on. That never happened before. I turned it off/on and performance returned but check engine light stayed on. I swung around to my friend who put a tester on it and got P1229 and P1111 codes. What have I got here. Any help/suggestions would be greatly appreciated

 

P1229 - Electronic throttle control circuit.
Probably the usual suspects either a crack in the breather pipe, dirty MAF sensor or dirty contacts on the throttle body connectors.
This is from my limited experience of similar problems.

 

See if you had TSB 303-58 done first. Under normal conditions you should have a DCT code of P0121. http://www.gusglikas.com/AutoRepTB.htm

 

The code I got, relative to TSB 303-58, was indeed P0121 - TPS signal out of range. It may be possible that others codes be generated... a simple cleaning (using contact cleaner/lubricant from Radio Shack) of the Throttle Position Sensor contacts, both in the unit and in the mating harness connector eliminated all my problems.

There are two other connectors at the throttle body - Throttle Position Motor and Pedal Position Sensor... probably wouldn't hurt to clean these connectors too, just in case.

 

Hi Gus...thanks for your reply. Not sure what a TSB is but the only codes that came up were 1229 and 1111.

 

Thanks Dinger...I'll try the cleaning option first. Seems the easiest and cheapest

 

OK..I'll try cleaning them first (when I find them!) and see if I can get away with an easy fix. Thanks again, I appreciate it

 

It is a Technical Service Bulletin that related to what the others are telling you to do with the exception of replacing the connectors. We seem to think that it is related to these connectors although it did not give you the P0121 code. It gave you a P1229

 

What do I need to get to clean and reseal this area? I have been getting this problem on occassion as well. Anyone have a photo to make sure I am cleaning and resealing correctly? Thanks.

 

Try this http://www.gusglikas.com/AutoRepTB.htm

 

It's easy to lose sight and panic when these things happen with our cars so I thought I'd share my story:
I had the engine go into failsafe mode -limping very slowly. When the ignition key was switched off and re-engaged it would resume and drive normally for about 5 minutes and then go into fail safe mode again. The engine MIL light then came on.
The idle speed was lower than normal and the car would stall quite often with this affliction.
I went to an autozone and they wouldnt give me the codes but diagnosed it as the MAF sensor. I was suspicious about this- as I had some issues with this a few months ago and solved these by simply cleaning. So I invested in the auto-enginuity kit and Jag module. This isn't as good as the ETAS ES-580 and INCA calibration equipment i was used to when developing these beasts but not too bad. The code I got was P1229 along with all the oxygen sensors.

I took off both connectors to the Denso throttle body, the TPS and the other (which I believe is the idle speed control but am not sure) and cleaned them and reconnected. As a sidenote- the Jags use the whole throttle as a long term strategy to control the idle speed and they use individual ignition per cylinder as a short term strategy to moderate idle speed. I presonally prefer the way BMW and Porsche do it with a sperate idle speed control motor and I'm not sure how I feel about using ignition to control idle speed due to its adverse impact on fuel economy, but oh well.
Anyway, cleaning and reconnecting these seems to have done the trick. Lets hope it doesnt come back.

Another note- regarding the reliability of Jags: The connectors involved are generic and the throttle body itself is a denso unit. The Denso unit is not a Ford unit nor used in any Ford vehicles- for anyone who may assert Ford have lowered the quality of Jaguars (in this case). I would be willing to bet a Lexus of similar age or the like would suffer similar issues, Certainly my collegues 2000 model year BMW 528i and other friends E39 M5 have had a variety of small maladies that had cost alot more to put right.