Yesterday my 02 XKR went into failsafe mode. After restarting the car ran fine. Did it again today and I had a shop check it out. They say the accelerator position sensor is defective. What is the difference between this sensor and a throttle position sensor. The shop tells me the entire throttle body must be replaced with the part costing $2500. After they cleaned the connectors the car goes into failsafe each time the car is started. After the shop cleared the codes the car started without going into failsafe. I haven't driven it to see how it does after clearing the codes. Any ideas would be appreciated. Thanks
Tommy

 

There are two sensors on the throttle body, one reports the position of the throttle pedal to the ECM, the other reports the position of the throttle valve. In between the ECM 'manages' the throttle valve in a drive-by-wire design.

Unfortunately, parts for repair of the throttle body have never been available. Must be a bench calibration issue as a couple folks that have attempted to adjusted their TB have been disappointed.

Used replacement from a wreaking yard is the most cost effective solution.

 

It is correct that the throttle position sensor or accelerator position sensor are part of the throttle body and only sold as a unit.

You can save lots of money, however by getting a rebuilt unit. Here is one source: http://www.jaytanindustriesinc.com/jaguartb.aspx .

I believe another forum member, 'Jaxkr' also has a good used one for sale. You can try to PM him.

I do not know what the standard labor cost is for this, but I have removed mine and replaced the gasket and I think it should be a couple of hours or less, max.

 

This seller on eBay rebuilds Jag throttle bodies. http://stores.ebay.com/ABS-ECU-ECM-E...REBUILD?_rdc=1 Also, they are just up the road from us in Rogersville, Tennessee (up by Kingsport). They might not specifically list it on eBay, but they can do it. Contact them directly through their website http://www.autoecu.com/

 

I got one from the guys in Tennessee awhile ago. It was around $500 if I remember. Car has run fine ever since. Turnaround was fast.

 

Update. On 2-11 the garage says they cleaned all the connectors and reset the ECM and asked me to drive the car before going with the throttle body replacement. I drove the car about 90 miles that day with no problems. On 2-12 I drove into town for about 5 miles and the car went into failsafe about 6 times. On 2-13 I removed the throttle body and cleaned it and also disconnected all the electrical connectors and sprayed then liberally with tuner cleaner, although they looked clean, and reinstalled everything. As of 2-15 I have put 145 miles on the car with no problems. I think I'll wait a couple weeks with no more failsafes until I consider the problem solved. This sure does destroy your confidence in the car. Thanks to everyone for all the info
Tommy

 

This TSB is not for your car but I would try cleaning the plugs first http://www.gusglikas.com/AutoRepTB.htm I hope this helps.

 

Actually I've only got the check engine light with that code a few times in the last few thousand miles but the way my ENGINE FAULT yellow light is getting a workout along with the POOR ENGINE PERFORMANCE red light on regular occasion, I seem to be about due for a rebuilt throttle body.

I can't help but play with it and I've gotten to where I can manage it pretty consistently. When the car is started cold I have little problem and if I ease it out, keep it moving, warm it up, then hit the freeway as I do twice a week, almost no ENGINE FAULT lights and it runs fine. Pull in, shut down and let it heat soak the TB for a half hour or so and that's when it's the worst. Back to the freeway and you'd think half of the injectors and or plugs were misfiring. Enough ENGINE FAULT lights and soon the POOR ENGINE PERFORMANCE light and message pops up. 20 miles down the freeway the TB has had enough cold air through it that the heat soak has been cleared up and it's acting more normal. Not perfect but good enough that I can pull off on an exit, shut it down for 30 seconds so the ECM buffers can drop the POOR ENGINE PERFORMANCE latch, fire up and back on the road with almost no yellow lights for the rest of the trip.

Stumble stumble, BUT, only in the bottom 10% of the throttle range. This is where the trouble always is and I'm mostly convinced it is one of the three electronic pieces on the TB; the APP, Servo, or TPS. I'm thinking it's probably the APP since I can flick the gas pedal and make the engine fault clear temporarily, but I can imagine even the servo could be simply gooed up after 140k miles and fourteen years. I've been pricing rebuilds and NOS new TBs on ebay but I still just want to open up the electronics on the TB to see if they need cleaning; no fun just swapping parts if I can't find the actual problem first... ... P-)

Followed Tim's trials and tribulations with interest as he finally got resolution with a freshened up ECM. That seems like a good plan regardless of need just to get updates he mentioned. I figure I paid less than 9k for this thing, once in a while I could make a car payment...

Right now this '97 is my 600 mile/week ride up and down I-5 and I hate to take it down and get back in the Suzuki for even a week or two..

Blue skies,
Mike

 

Morning Gus
I cleaned all the connectors with lots of tuner cleaner and all the connectors closed securely. On the way to work this morning I got failsafe about 8 times and the car ran normally. At the shop codes of 1121 and 1122 show up. The thorttle body is coming off for the rebuild shop today. I'll keep everyone posted. Thanks
Tommy

 

Update
On 2-17 I had the throttle body rebuilt by ASI in Rogersville, TN for just a little over $500 and it was done in about an hour while I waited. Installed on 2-18 and no failsafe yet.

 

No harm in trying!

 

Way to keep your thread up to date! Your a model member.

 

After installing the rebuilt throttle body on 2-17 the car has performed beautifully until today. Going thru a parking lot I noticed the failsafe warning along with check rear lights. Always before during failsafe the engine power was greatly reduced and appeared to not run on all cylinders. This time engine appeared normal except for the warning. I pulled over and checked the light with all working normally. I restarted the car and drove 100 yds and same warning appeared. I again restarted the car and drove for 3-4 miles before it reappeared. The next time I drove to Autozone and checked for codes and got P1642 and P1111. Now the amber check engine symbol appears but no failsafe or check rear lights warning. I have not checked for maxumum acceleration but the engine appears to run normally. Any ideas?

 

I'm guessing that you have a bad brake pedal switch. It's completely unrelated to the throttle body. Do you also get a cruise control not available error?

 

I agree, my XK8 is a real handfull to keep running. I originally bought mine with 44,000 miles and intended to use it as a daily driver. Frankly, it's just not up to the task, although I may have asked too much from a 10 year old car...

I still enjoy owning it, but for reasons different than I thought when I bought it. Today I get considerable satisfaction from diagnosing and solving problems - this forum is a great resource in that regard. You'll get to the bottom of your problem with the help here!

 

Good morning Reverend Sam
There is no cruise warning, only Failsafe and Check rear lights. I am starting a 250 mile drive to return home today and we'll see how it does. When I started the car this morning there were no warnings and no check engine light. A shame it's such a fine car but its beginning to test my confidence. Thanks
Tommy

 

Couple questions. Where is the brake switch and how do I test it? Thanks
Tommy

 

Here is a link to a good discussion on the brake switch: Brake Switch Replacement How-To (W/ Pics) FAQ - Jaguar Forums - Jaguar Enthusiasts Forum

It is a double pole micro switch, one side normally closed, the other side normally open. The ECM gets confused if it doesn't see the open/closed or closed/open combination.

 

Update
Although I don't get a cruise warning the cruise is involved. I normally leave the cruise switch on the console on and just engaga cruise when I want it. This morning with no warnings shown I engaged the cruise and it immediately disengaged. I turned cruise off via console switch and back on then engaged cruise and it worked for several miles until I disengaged it via brake due to traffic. A couple miles later with cruise on but not engaged I got the failsafe and rear lights warning. The cruise light on the console went off and couldn't be turned on. After turning ignition back on the warnings went away and I didn't turn the cruise back on. I have driven about 10 miles with no warnings. I have about 200 to go so will keep you posted. Thanks

 

it is definitely the brake switch, you bettin against the reverend?!?