2002 XK8, 118,000 miles, basically good condition, all garage kept. I got the dreaded gearbox fault, ASC NOT AVAILABLE and P1632 . It also exhibited P1222 Pedal position sensor B circuit low input and P1260 security input. The battery voltage is 12.5 and starts the car easily. Battery is 10 months old. Voltage with engine running, lights on is 13.6. Is that too low or am i on the wrong track? I had the transmission rebuilt at 105,000 miles. Should I have the throttle body rebuilt?

Thanks in advance

David

 

Hi David,

It's late here and I'm falling asleep, but the first thing I notice is that all three of your DTCs have to do with communication to the ECM. It might be worth disconnecting the vehicle battery, then disconnecting the ECM electrical connectors and inspecting for any signs of corrosion or water ingress.

Another potential cause is corrosion on the ground points referenced by the ECM, which are inside or just outside the plastic box that contains the ECM. It is worthwhile to disconnect the grounds, clean the eyelet terminals, nut, washers, and threaded stud and reassemble. Don't overtighten the nut - just make it snug.

If you don't see any problems at the ECM or grounds, it would be worth observing the voltage sag while cranking. An analog voltmeter is faster-reacting than a digital meter. If the voltage while cranking sags to much below 11 volts, spurious codes can be triggered.

The DTC Summaries (attached) gives some possible causes of your codes. I am also attaching the wiring schematics so you can see the circuits that are triggering the codes.

Cheers,

Don

 

Don, Thanks again for the help. I checked the connections at the ECM and they all were pristine. I replaced all the wheel speed sensors (on a whim from previous research), cleaned the throttle throat and finished a few other things (d@mn shock mounts) and took it for a spin. Same issue but now the code is P1222 (throttle position sensor) and B1222 (right seat heater output?!?). I took it back to check the throttle position sensor and found that the clip that holds the connector tight was broken and the connector was not tight. I put a zip tie on it and it seemed good for three days. I thought i had it licked. On the way to work this morning, I got the ACS, GEARBOX FAULT and limp mode, but no codes. At the next stoplight, I put it into park (I heard a subtle but unnerving clunk doing that) turned it off and back on and it was fine til I got to work. I still doubt that its a weak alternator, but could easily be wrong.

Would a shop with Jaguar software be able to tell me anything helpful?

 

Hi David,

Your situation could be similar to what Joe is dealing with. See his thread here:

https://www.jaguarforums.com/forum/x...w-what-293341/

You might want to do the basic electrical connection maintenance that I recommended to Joe.

Some auto parts stores have good battery-charging system analyzers and can test your alternator in the car to see if it is underperforming, has high AC ripple, has a dead diode, etc.

Don't worry about the seat heater code for now.

As far as I know, the GEARBOX FAULT and RESTRICTED PERFORMANCE cannot be triggered unless faults are detected that should also trigger Diagnostic Trouble Codes (DTCs). When you have the GEARBOX FAULT, there should be at least one code stored in the Transmission Control Module or Engine Control Module or both. The code may be a Powertrain (P-prefix) code or a Network (U-prefix) code if it is related to CAN bus communications.

If your scan tool can display Live Data, see if there is a Parameter I.D. (PID) for throttle position sensor. If you can view that signal with the ignition on but the engine not running, observe the signal as you slowly depress and release the accelerator pedal. The signal should vary smoothly with no dead spots or glitches.

When I am having these kinds of problems, I keep clearing codes and re-testing to be sure I'm only chasing persistent codes that are directly related to the symptoms of concern. The DTC Summaries I posted earlier give the definitions, possible causes and consequences of each DTC, so you can often tell which ones can cause Restricted Performance so you know what to focus on.

Cheers,

Don

 

Thanks again, Don. I will drive deeper into the grounds and connections. It's not showing any CEL or codes of any type with this most recent misadventure. Thats why I was wondering if a Jag shop would be able to read the TCM for any error codes that don't show up as CEL.

I do appreciate all the help.

 

Sorry, I meant to address the question of a Jaguar shop. A good independent shop may be equipped to scan all the codes, and perhaps to do additional computer diagnostics. Many Jaguar dealerships no longer have the IDS or SDD diagnostic systems that were used when your car was new and still under warranty.

But since your scan tool can read Body (B-prefix) codes, then presumably it can also read Chassis (C-prefix) and Network (U-prefix) codes.

Regarding your P1222 code, here's what the DTC Summaries have to say:




Check the Workshop Manual to see if there are pinpoint tests you can conduct to find the cause of the P1222 code.

Cheers,

Don

 

If I'm not mistaken the pedal position sensor is internal to the throttle body. I a poor connection is ruled out, that sensor can't be easily serviced.

 

As you have already suggested the very first thing to do is check the live data for what the car thinks the Pedal Position Sensor is doing. Next check the wiring to the sensor with a multimeter at the ECM end. The connectors to the sensor have to be the number one suspect here if there is a problem.

And as a public service announcement it's easy to confuse the Throttle Position Sensor with the Pedal Position Sensor - to the OP make sure you know which is which when testing.

 

The saga continues. Please forgive as I travel a lot and I check things as I can. I have an Ancel FX2000 OBDII/EOBD+CAN. The live stream is limited and I dont know if its me or the Ancel, but it does have a DATASTREAM mode. With that, I was able to read the wheel sensors. With that, it was showing that the front left wheel was doing 36.83KPH, front right 0.0, and both of the rear wheels were reading 146.25. Obviously, this wasn't correct as the car was in the barn at the time, idling. I had replaced all of them as part of this recent issue (with non-Jag parts).

It also indicated that there was a "permanent" code P1632 that read "Smart generator faults sensor/circuit./Generator charge system failure/generator i loadi feedback circuit failure./Smart generator output circuit." Weird typos compliments of ANCEL.

There was also a P1794 "Battery supply malfunction." Last time I checked the voltage with engine running, I was getting 13.6. I realize there could still be a voltage regulator issue, so I am planning on doing the alternator now.

Please let me know if any of this generates new ideas. Its the best handling car I've ever had. I miss driving the old girl, but the bloody "limp mode" irritates the **** out of me.

David

 

Don't bother with the generic description the code reader gives you, search for the code on this forum and see what it actually means. Use the search box on the top right - that will search this X100 group only and give you very specific results:-

 

Hi David,

The best source for the Jaguar definitions of Diagnostic Trouble Codes (DTCs) is the official DTC Summaries manual for your model and year. I am attaching a fairly complete version of the manual to this post. You can also download the Powertrain section at the link below:

Jaguar X100 DTC Summaries 2001

P1632 shows up with multiple defnitions, so you have to use some judgement as to which defnition best fits your symptoms. It is also important to note which computer module is reporting the code. Some codes can be reported by the ECM, TCM and ABS/DSC Module, for example. Here are the published definitions and possible causes of your codes. They all appear to be related to the Transmission Control Module (TCM) or Controller Area Network (CAN):







Regarding your alternator, I would recommend having it tested before replacing it. Many auto parts stores can test it for free while it's still in the vehicle. There are other possible causes of your symptoms, and throwing new parts at the car without proper diagnosis gets expensive and may not resolve the problems.

Cheers,

Don

 

Cleaned the ECM contacts and hard reset (grounded the positve cable) and have been using for short trips daily.

Definite improvement, no LIMP MODE or GEARBOX FAULT anymore, but she just doesn't feel right. A slight shudder in the engine, the idle has dropped to about 600 RPM (normally 8-900) and feels slightly sluggish. Not as definite as a miss in the firing pattern, though. Still no CL or codes. I haven't done the alternator because this doesn't feel like an electrical issue. I had that TPS sensor code earlier and i wonder if it is related.

Any suggestions will be apprecioated.

 

I can't remember all the details you've been dealing with, but a couple of questions come to mind:

1. How recently had you purchased fuel before the onset of these symptoms? Is it possible you got gasoline that was contaminated with water?

2. How long since you've done a basic tune-up (spark plugs, air filter, fuel filter, clean the MAFS, clean the engine ground strap and other critical ground points, etc.)?

3. If your scan tool can read Live Data, what are your Short-Term and Long-Term fuel trims (STFT & LTFT) at idle, 1,500 rpm and 2,500 rpm?

Cheers,

Don

 

Thanks so much, Don. As discussed, I have an ANCEL FX2000 which is supposed to read live data, but I have not fully mastered it yet. Its about time for a tune up, so I will dig into and check back. Thanks again, David

 

My XK 2003 was a mess with codes all over the place including gearbox fault. Replaced the following; Battery (old), cleaned plug to gearbox (oily, -ECM-Gearbox communication erratic), and the generator (failed, -voltage randomly drifted outside tolerances for the electronics in the gearbox). Most likely it all started to go south when someone tossed the cooling duct to the generator (it has no internal cooling fan) and also the famous brake light switch (micro current leak through the tiny switches). After this, all codes and struggles gone! (fingers crossed)

Personally i have a little hard time to believe that a car that just sits for a while **** itself and fall apart, it just cannot happen.. Bad battery, fuel pump seize, and really bad fuel, a few plugs that needs to be re-fitted -yes. But for sure, if a car sits outside for a prolonged time, electrical issues related to corrosion will occur on top of fuel supply problems.

It is also sometimes easy to overthink problems.. fancy OEBD readers and all, it usually boils down to quite basic, hopefully not to expensive things..

/E