I took my car out on this beautiful day to get a few errands done and knock the dust off a little. I was thinking wow this car has been running flawlessly not 2 minutes before this happened On the way home I needed to make a left on a busy road so I had to wait a bit when I accelerated to go I got an Eng Fault, and DSC Fault and high idle around 1100 rpm so I got it off the road and turned off the vehicle. I was only a mile or so from my house so I restarted it and everything was great till I turned into my neighborhood and it faulted again (actually twice) before getting back to my house.

When I got back home my scanner easily found a P0121 throttle position sensor. The forum threads I read all pretty much said check and clean all the TB plugs and connections. So I did that and cleared the codes before another spin around the neighborhood which was unsuccessful (same fault). So I did the plugs again and did a little more in-depth look at all the wiring and this time shortly after starting the car while idling faulted again. My understanding is if it's not the plugs more than likely it is the throttle body. Joy

A couple of quick things, this is a 2003 XK8 conv. My battery is perfect and always on a tender when not in use. I'm aware of ASI in TN and will use them if I have to have the TB rebuilt.

Questions:

If the TB sensor is bad why can't it be changed to correct the problem?

Does anyone know the Part # for 2003 4.2l? I hate owning a cross over year.

Can you think of something for me to check or any suggestions?

Thanks a ton guys

 

I think I figured out the sensor replacement it's a Denso 198500 3300 that's what is installed in my car now. Though this sensor is not showing as compatible with my 2003 4.2 but that's what mine reads so I don't see a problem using it? Also my car build date is 05/03

Am I missing anything?

 

If you can;
start the car and if it drives fine, make a left hand turn. If you then have a fault, replace the left rear wheel bearing.
The wheel sensor looses its sign and causes many strange error messages and faults.
wj

 

You may struggle to find a genuine OEM Denso part. I can't find any reference to it (or any TPS) on the Denso site.

Lots of clones out there, some as cheap as <$20.There appears to be a crossover with the X-type and later XJ8 (aluminium bodied) so sourcing one from a breaker may be an option.
Either way, it's a bit of a lottery

The 2003 DTC list shows how to test without driving the car:

 

That is really a good thought because I was wondering if the fault was only occurring after turning left. Unfortunately, the faults seem to be unrelated to the direction of the vehicle I'm getting it right, straight and even at idle. However I will check the wheel bearings manually while trouble shooting. Thanks for the suggestion.

 

Michael we are thinking alike regarding the sensor. If it's just the sensor wouldn't it be worth trying a used Denso or a new clone? It isn't hard to get to or change and at the end of the day a throttle position sensor is not that complicated.

Also, while I was searching online for an exact part # for my exact car it was a crap shoot of contradicting information. So I think it's logical to use the part that is already there. It seems this Denso 198500 3300 was used in the 2004-06 XK8, 2003 XJ8s so, since the build date on my car is 5/03 it's extremely likely that my vehicle was part of the change over that occurred in later 2003 production run that included the 2003 XK8.

Is it a lottery? Sure it is but the difference in money makes it worth a try. I would rather try a another sensor for $50 (or less) and see what happens. A rebuild will be in the $500 range and I don't want to be the guy that has it rebuilt only to find that it did not correct the problem.(we have all seen it). If I'm out $50 to find out that's OK but if it needs to be rebuilt I'll send it to ASI and feel better about writing the check (figuratively lol).

Michael, I also retired shortly after you did and I like it when people send me checks for sleeping in. I'm staying busy as ever as I'm sure you are too. But, you don't have to.if you don't want to period. Hope all is well my friend..

 

So after a day of searching I purchased a brand new Denso 198500 3300. Of course it's in Taiwan and shipping is $25 (returns excepted) but, under $65 to my door step sounds good to me.

​​​​​​

NEW GENUINE / OEM 198500-3300 for THROTTLE BODY XR845053 XR843535 1X43-9F991-CE

$35.00

 

I agree it's a cheaper option than going for a TB rebuild at this stage, although (if my understanding is correct) a replacement TPS may well throw the same code if the two outputs don't track as the ECM expects. I wonder where the rebuilders source them?

If you come across an OEM in a breakers yard I'd be tempted to grab it even if the one you've ordered does the job.

Curious:- can you induce the fault by following the procedure in the DTC 'monitoring conditions' ? That would give you a pretty definitive cause.

I worked six years beyond official retiring age, but TBH I was winding down for four of them. I have no trouble filling my days, but all is good. I hope it's so for you too.

 

This part and all the parts this seller has look totally legit. What do you think? I'm staying positive lol

https://www.ebay.com/str/vssenginemanagement

 

my parts purchases on eBay have soured me on taking more chances there.

I bought the transmission plate on eBay, it was shown with a Mercedes box and it had the Mercedes logo and part number stamped on it

it arrived in a generic box and the part was 100% counterfeit. Now I have a transmission which displays random & spurious HOT messages when I know it’s cold. Unfortunately I tossed the original OEM part before the new one started acting up.

its worth it to me to suffer the high prices with the real factory parts and not be plagued with the fake counterfeits.

Z

 

Hey Z

I wanted a new part and they had it I would have loved to have found the same part in North America and paid twice for it but that option wasn't available. I'm not a big fan of counterfeit items either but I think we have all been had many times and didn't even know it.

​​​​​​Update: this company had to cancel my order because they are not shipping to the US at this time. So now I'm buying a used Denso unit for about the same price.

 

I replaced the TPS on mine before I swapped throttle bodies. I bought it off of Amazon. IIRC it was around $30. It worked fine, You DO have to perform a hard reset after installation. I also replaced by entire TB with one from a scapped XJS and it had a generic aftermarket TPS and it's also working fine.

BTW, when I got the same symptoms as you I disconnected the connectors and soaked both with electrical connection cleaner and the problem went away. Try that first.

I changed TPS for other reasons, not the P0121 code.

 

used tbs to steal a tps out of are dime a dozen. all the 32 bit cars use them, x400, x350, x202

 

Hey Y2K and xalt

​ ​ ​ ​ ​ ​ ​ That's what it looks like to me these parts seem to be everywhere and extremely reasonable. I would definitely put throttle body and tps sensors in the category, "it's worth it to try it". It's also great that good companies like ASI are out there to help when we decide it's time for someone else to do this and get it right lol.

Update, I ordered a Denso sensor from a scrap yard in Ca for $60 I'll let everyone know how it goes. Thanks again guys

 

I had a journey getting a 198500-3250 TPS for a 2002 XK8. Neither of the knock offs from Amazon worked. When tested the resistance values were way off. Used Densos are $250 on eBay. @hispeed42 was gracious and sent me one he had laying around for shipping and I tipped him enough for a high quality 6 pack. On mine you need a 5-point torx to unscrew. Guessing same on yours. Next time in a salvage yard, I'll be looking to pick up a spare.

 

I think you are better off with a used working OEM Denso part.

best of luck going forward with the repair.

Z

 

Hey Michael

I'm reading a lot of threads and pouring over information most times conflicting about the 4.2L throttle body and the TPS functions.

They say: No way to adjust the sensor because it is calibrated as a single unit.

Well the sensor does have adjustment slots on the sensor body soooo wouldn't that make the sensor adjustable?

The 198500 3300 TPS is very common and used on many 2003 and up vehicles.

I realized that many who had been successful in changing the TPS were on earlier 4.0 model years.

It would be great if a 4.2L owner could tell me they've been successful attempting a swap on the TPS.

looks adjustable to me?

Thanks all

 

[QUOTE=Shoreguy;2872859]
looks adjustable to me?

/QUOTE]
I recently replaced on ‘02 and adjusted the idle by rotating around the little bolts. Too far one way died, too far the other idled at 1000+, in between just right.

 

My understanding is the 02 were the last cable driven throttle bodies. The 2003-06 have the electrically driven throttle bodies that are supposedly calibrated as one unit at the factory. However it's still just a TPS installed at a certain mark? Well I should have my part on Tuesday and I'll let ya all know how it goes. Peace

 

All model years are fly by wire in that the accelerator pedal controls the throttle butterfly electronically. The earliest cars had a mechanical guard/physical override, but the normal operation is still 100% electronic.

The TPS is adaptive, so you need to physically set the position to get it roughly correct and then the car will learn the new limits (hence the hard reset mentioned above).