I have been tracking down a P1224 fault code. According to the manual this revolves around the TPS. Symptoms are erratic idle, high idle and faulty shifting at low speed or slow acceleration.
I have done the following :
1. cleaned all wheel sensors and connectors.
2. cleaned all connectors to the TB.
3. Cleaned all connectors to the ECM.
4. Cleaned all connectors to the TCM.
5. check the 30V fuse to the TB - it's ok.
6. Cleaned the TB throat & butterfly valve.
7. Battery is one year old, has full charge. Ground is good and secure. All cables clean, good condition, no corrosion.

Next thing, once I get the tamper proof hex wrenches, is to clean the TPS itself. (what idiot Jag engineer thought of putting a cover over the TPS and securing it with tamper proof bolts?)

However, thinking I may have to replace TPS I have been trying to track down the part number. The 97-98 models are difficult and I have been getting conflicting information. Also, there seems to be no substitutes and new ones cost a fortune - $365, as much as a complete TB rebuild. Here is the Jag number : JLM12074 This has a 4 pin connector.

My question is : does anyone know the Denso number, assuming it is a Denso part? The 99 on use a Denso, so I am assuming the 97 uses one also. It appears that the 97-98 DOES NOT use the same TPS. Please correct me if I am wrong. You can pick up the Denso 198500-3250 for my99 - 02 cheap on eBay. But finding a 97-98 TPS is very difficult.

To add to the confusion, it seems that the 99 TB may be used on a 97? If so, then the 99 TPS should work on a 97 TB??

The JTIDs also notes that throttle motor may be the issue but I don't think so. I could be wrong. Here is the complete list of possible causes that JTIDS lists :

Throttle position adaptions not performed after battery disconnect
TP sensor disconnected
TP sensor to ECM sense circuits open circuit, high resistance
Throttle motor power relay failure
Throttle motor power relay to ECM circuit fault
Throttle motor power relay power supply open circuit
ECM ground circuit fault (relay coil drive)
Throttle motor to ECM drive circuits open circuit, short circuit, high resistance
Throttle motor failure
Throttle assembly failure

Last, if anyone has any suggestions as to what else could be causing a P1224 fault code I would appreciate hearing it.

thanks

 

You've already got the list of 'possible causes' from JTIS. When I got P1224 on my 2001 XK8, I was able to clear it a few times but it went from first showing up to total failure in less than six weeks of daily driving.

This thread details the subsequent investigation steveinfrance did on my failed TPS. We wanted to know exactly why they fail:

https://www.jaguarforums.com/forum/x...acement-77560/

This one discusses interchangeability and other possible sources of a replacement:

https://www.jaguarforums.com/forum/s...solved-138182/

Graham

 

The throttle body for the early cars is a totally different beast. The TPS is a Hall-effect device which should be much more reliable as there's nothing in theory to wear out. Sadly Jaguar negated any value this might have added by introducing two rotary potentiometers to monitor the accelerator pedal and 'mechanical guard' positions. I have never been able to find part numbers for any of these sensors.

Having said that, they don't seem to be as problematic as the later ones, although that may just be because there are fewer of them.

ASI can test/rebuild the TB, or you may be able to source one from an earlier XJ8.

Shot in the dark - the ECM on the 97 is notorious for all manner of weird and not-so-wonderful issues. Take a look at Bradstuff's thread. He was chasing a P1224 (albeit with other codes also), which proved ultimately to be the ECM:

https://www.jaguarforums.com/forum/x...1/#post1598345

 

"two rotary potentiometers to monitor the accelerator pedal and 'mechanical guard' positions"? Is that the sensor located opposite the TPS near the throttle cable?

 

I read the first article, which I thought was excellent, although some of the electronics was a little over my head. I also read several other articles about the TPS. My impression was there are no substitutes for the XK8 TPS.

My real problem is how to test any issues for the throttle motor. I think I may just end up sending the TB off to get it rebuilt.....I just want to eliminate everything else before spending $400.

 

Oh, yes, my car only has about 55K miles on it.

 

Oh, yes, I also have a P1779 DTC. My assumption is that if I fix the P1224 code the P1779 will be cured also. Perhaps I am wrong?

 

Could be being over optimistic .....



Graham

 

Yes


I don't want to send you off in the wrong direction, although bear in mind that the throttle actuator is driven by the ECM. A search on P1224 brought back a few hits- one by Pristine97xk8:
https://www.jaguarforums.com/forum/x...1/#post1393262

and this by gardcyl:
https://www.jaguarforums.com/forum/x...7/#post1129222

The ECM was implicated in both cases.
Given the number of members' reports of spurious codes thrown when their early ECMs were ultimately found to be failing makes it a distinct possibility.

One of those times when it would be really useful to be able to pull the relevant part off a shelf to do a quick substitution check. Failing that, you have to troubleshoot by elimination. ASI offers a rebuild service for the 97 for $159, and I believe they will test for about 1/3 of that, either of which is considerably cheaper than the TB rebuild. From what I can gather, it wouldn't be money wasted as it's a case of when and not if they fail.

Take a look at the above threads and see what you think.

 

Current ASI pricing : ECM TEST = $55 // ECM REBUILD = $350
THROTTLE BODY TEST = $55 // TB REBUILD = $289

 

Odd. I got the $159 yesterday from ASI's fleabay ad that came up in a search for TB repair:
https://www.ebay.com/itm/1997-97-JAG...-/111697231903

which is why I suggested it as the cheaper option. Their own site, autoecu.com, quotes the price you have for the TB.

If you're comfortable with removing & opening the ECM you can do a visual inspection. Of course, it may be faulty and still look OK, but if any of the internals have done their 'leaking goo' party trick you at least have a pointer.

I'm no advocate of the 'just throw parts at it' approach, but you have to eliminate the other suspects somehow now after all the basic checks.

Sorry I can't be more definitive.

 

Thanks for the extra effort michaelh. I appreciate it.

 

Hey Green!
i had the same exact issues with my 97 XK8 a month ago. I read they a number of threads and the common link was the ECU. I pulled the ECU, opened it and found this. Found a $169 eBay from ASI. Got it back in 4 days and it’s purring ever since. No codes and dare I say, it’s never run so well.

Nick

 

Ok, guys, just pulled my ECU. First thing I noticed was a hand written statement on the outside : REBUILT 8-14. So, it was rebuilt about 3 years ago already. As soon as I opened it up I smelled burnt electronics. Took me about 5 seconds to spot the burnt capacitor just like the photo provided by spinedoc2304.

So, it is off to ASI for repair. Thanks for all the help. guys. I love my Jag and I love this forum.

Charlie Harper

 

One thing, on my car the ECU is not secured in any manner. The only thing holding it in place is all the attached wiring harnesses. Is this normal or am I missing a tie down of some sort?

 

Well, bad news, ASI told me they can't repair my ECU. To replace it they want $1400. A quick look on eBay and the cheapest used one is $900. Ouch. 97 is a bad year. 99 --> on you can get for as little as $50. So, I have to start looking around. Anyone know where I can pick up a 97 ECU cheap I'd appreciate the lead. Part # LJA1410CA

Attached are some photos for future reference as far as unrepairable ECUs.

 

Hi greenforest,
It's never quite the same looking at a photo as having the offending item in your hands, but I'm surprised that ASI has given up on the repair so easily. Perhaps rebuilds are limited to the mostly obvious and simple, although that's understandable if they don't have the schematics.

The damage is very localised: I would ensure that you get the unit back, and let a good electronics tech take a look. Problem is downtime, and I guess that in SF there's no need to put the cat in storage over the winter! If you can tolerate that I'd certainly explore other possibilities given that limited supply has pushed the replacement costs skywards. There doesn't appear to be a crossover route from the XJ8 with these modules either.

While you're seeking a solution, you might spend a little time with some isopropyl alcohol and Q-tips. Try (gently) to clean the crud from around that capacitor. It's hard to tell whether the board is damaged or it's just the cap's contents.

 

Here is a direct quote from ASI after I sent them the photos :

Hi
That is definitely not repairable ,
When the burn is that severe under the capacitor the pcb internal grounds are severed within the substrate of the pcb
This ecu is extremely rare and expensive ........

I suspect ASI knows what they're talking about, although I will contact a couple other repair places. Meantime, I am going to keep looking for a used ECM. The other used one on eBay is going for $1700!!

 

ASI will doubtless have seen many of these modules and the varying degrees of damage they sustain and yes, multilayer pcbs present particular challenges. I'd want to see the reverse of that area before totally condemning it. Don't throw it away just yet.

Certainly put a call out in the 'wanted' classifieds. There are several members parting out XK8s.

Perhaps drop member XJsc-guy a pm:

https://www.jaguarforums.com/forum/p...0/#post1771767

 

Ok, tell me if I am correct : the rebuilt ECM that was in my car was part # LJA1410CA.
However - the last digits of my VIN number are : 012091
So, if I understand this chart correctly :

From the Parts Catalogue, these are the early ECM's by VIN range and N/A or S/C:

to VIN 018107 : LJA1410GA
from VIN 018108 : LNC1410GA
from VIN 019346 : LNC1410EA (supercharged)
to VIN 020733 : LJA1410CA (except supercharged)
from VIN 020734 : LNC1410BB, LNE1410BE (except supercharged), LNC1410CA (supercharged)

Given my low VIN number, the proper ECM for my 97 XK8 should be the LJA1410GA not LJA1410CA that was actually in the vehicle. If this is correct, then that might explain why the ECM burned up so badly.

Does this make sense to anyone? Am I understanding the part chart correctly?
Thanks