Thought I’d document a problem and solution that cropped up on my 2017 F Type R. A few months ago, I got a check engine light (CEL). Used a my Bluetooth code reader and got a couple of codes about accelerator low-position calibration error. Shortly after, I got a restricted performance message and the car was in limp mode.

I used my reader to clear the codes, and all was fine for a week or two. Problem occurred again, and this time as a precaution, I ordered up another accelerator pedal assembly off eBay for around $40. Cleared the codes, was fine again for a few days. Over the next 2 weeks, this problem reoccurred with increasing frequency. Finally a few days ago, once I cleared these codes, they immediately reappeared with the “restricted performance” message and no way to get out of limp mode. Whatever was failing - probably with the accelerator assembly - had finally bit the dust.

So, I decided to swap out the accelerator pedal assembly. Fairly easy job. First, unplug the battery. Then remove the three torx (T30) bolts under the dash and swap out the pedal. I then cleared the codes - which stayed cleared - and did another unplug/replug cycle on the battery.*. Problem is now resolved. No issues and car has been solid for a couple of days. Obviously, the issue was the electronic throttle assembly. I’m guessing the potentiometer got out of range, either due to contamination or wear. I have read of this issue on a few other Jags. FYI.

Edit: Update. I decided to take apart the old accelerator. Pic is below. It uses hall-effect sensors for throttle position. Those are 3 magnets on the pedal assembly. Now, I noticed my assembly was missing one of the torx bolts that holds it together. There was noticeable play in the housing. This is likely the source of my problem. Hall effect sensors are very sensitive to position. The lack of this bolt meant the sensor wasn't properly postioned. Someone had this pedal open in the past, and didn't properly reassemble it. The new pedal I installed fixed this problem, obviously.

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*For those unaware, there’s a nasty bug in the OBD-II port on our F Types. If you plug in any device to the OBD-II port, it puts the car on a permanent-on condition which will rather quickly drain your battery. You know its in this condition as the warning triangle light on the hazard lights button will remain illuminated. The solution to this problem is to unplug/replug the battery. You have to do this anytime you use the OBD-II port.

 

Awesome, thank you for posting the solution.

 

Regarding your comment shown here below;

' If you plug in any device to the OBD-II port, it puts the car on a permanent-on condition which will rather quickly drain your battery. You know its in this condition as the warning triangle light on the hazard lights button will remain illuminated. The solution to this problem is to unplug/replug the battery. You have to do this anytime you use the OBD-II port. "


Does this also apply to when taking the car to the state motor vehicle inspection station for the car's safety inspection?

Thank you!

 

The OBD drain issue isn't "whenever you plug into the port" but when a particular device doesn't close the session correctly. Smog tests apparently will trigger the condition. Mine's been plugged in many times in UK garages and I've never had the drain condition. Please don't peddle misinformation.

 

Respectfully, I didn't peddle 'misinformation". I provided an accurate description of an issue including an indicator of when the issue arises (the illumintated warning triangle), and the solution. This is well-documented right here, and among that documentation is the finding that it results from OBD readers not properly closing out the query with the Jag software. Most readers won't do this. The readers at the dealers avoid this problem, of course, but most others do. I've had this issue everytime an OBD reader is plugged into my car, including the emissions inspection station readers.

 

Sorry but I have to agree with scm, this problem most definitely does NOT occur every time you plug something into the OBD2 port.
At least not on every F-Type.
I for one have NEVER had this problem and I have plugged numerous things into the OBD2 port, most commonly my iCarsoft LR V2 code reader hundreds of times.
Less common plugs I have used are the VAP tool and an ELMs 327 dongle.
Yes it does appear to be a problem with some/most US state based emissions tests but luckily for me there is no such thing in my neck of the woods.

 

I'm from Morris Co NJ as well. The state inspectors in Randolph haven't caused a battery drain 2 of 3 inspections.
Our older OBD scanner hasn't stopped shutdown, either.

The inspector that did, probably didn't shut down the reader (they were rushed). So, it is wise to verify that the HAZARD triangle goes off after 15 - 20 minutes.

PM me if you want to join me with an Adult Beverage while we wait for your light to go off. (Sip, don't chug!)

PS: The GMC dealer 0.5 miles from the inspection station has an F-type in their used car lot.

 

Hmm... I thought this was a universal problem, but now appears to be related to the software in our individual cars, so I'll add my $0.02 here.

First, I bought my car in July 2018 after it was returned to a Jaguar dealership in southern CA (that will go unnamed) under the Lemon Law. The car repeatedly had dead battery issues, the dealership had replaced the battery in the car 5 times during that process but could not figure out what the problem was.

I purchased the car from the Jaguar dealership in West Palm Beach, Florida (who I have nothing but good things to say about) who purchased the car at auction. They did a significant number of upgrades/fixes to the car prior to my purchase including of course, replacing the battery again for the sixth time.

After I purchased the car and became aware of this OBDII issue and the battery reset from this forum, I have watched the red hazard triangle after every OBDII connection closely and can say that without question, every time something gets plugged into my OBDII it requires a battery reset afterwards. I have two different OBDII readers, its happened every time I have gotten the car back from the dealership and it has happened every time I have taken it in for emissions testing.

With the forgoing being said, I still have the sixth battery the West Palm Beach dealership put in may car in July 2018 and it is still working perfectly because of watching the hazard triangle and using the battery reset fix.

 

There was a software update for the older cars that was supposed to mitigate (or lessen) the OBD-II disconnect issue--I don't know how successful it was. I know I never had this issue in my 2018 nor my 2023, including numerous connect/disconnect of tuner devices, Bluetooth code readers, and yearly state inspections at multiple locations.

 

Adding a bit more info for future owners. After a week or so, I got another limp-mode and CEL. This time, the code was for low-input error in the accelerator sensor (for circuit E, see below) I cleared this, and the error would return within a day or two. I hooked up a real-time reading of the accelerator postiion output, and noted that the baseline was reading about 17% open. It would vary by perhaps 0.5% depending on time, temperature, etc, and the code seemed to occur when the baseline reading was on the high side.

Anyway, I got to thinking that these sensors are probably calibrated at the factory. I reassembled my old accelerator (pictures, above) with a combination of epoxy and screws, and reinstalled this into the car. Now, the baseline reading was 14% open. Since I reinstalled this, I haven't had a return of the low-input error CEL and limp mode.

Lesson: the accelerator is a digital device that likely is calibrated as part of initial assembly (and there may very well be a calibration procedure in the Jaguar Shop software, which I don't have access too). Just replacing the hardware may or may not work. It's worth reading out the accelerator position values before replacement, so you have a reference. In my case, there was a pretty substantial difference and this lead to another problem. FYI.

 

Interesting. I’m looking in the repair manual…

So it’s an analog sensor. This is a pretty clever way of ensuring the validity of the position reading.

Here’s a link to the workshop manual…
https://www.dropbox.com/scl/fi/o6d1x...k7yc02pyx&dl=0

 

Thank you for this. The analog output heads to the ECM, where it is digitized. I'm still nearly certain that there's some sort of calibration done as part of all this. I've had 2 separate accelerator modules installed in my 17 R. As noted above, one read 17% baseline, the other 14%. I was getting low input errors with the 17% module.

 

Yeah, I was looking to see if calibration was mentioned, I didn’t see anything.

 

Another update. The car continued to throw the P2127 code (throttle position low input). Car goes into limp mode when this happens. Until recently, I could clear this with my reader. About 3 weeks ago, it was getting more difficult to clear. In some cases, I'd have to drive the car in limp mode a bit, then it would clear. Strange. I decided to try a pedal commander box, to rule out anything electrical with the accelerator pedal assembly. Installed this, and it worked great. (side note: it really does provide a more sporty response and the Type R feels far more "peppy"). Anyway, after about a week, the car again gave the P2127 and went to limp mode. The combination of the increasing frequency of the problem and ruling out the pedal side leads me to believe its the throttle motor or throttle motor sensor. So....

The next step was replacing the throttle body. Ordered up a throttle body (off eBay, $50, hey, I'm cheap) and got that installed. Tricky install, as you have to remove the upper Y-pipe and also attach the cooling system to the throttle body (to prevent icing in certain conditions). Got it all installed and buttoned up. Car started right up, no codes! That's a victory, right there. A couple of test drives, no leaks. Another victory! So far, no codes but its only been a few days.

I took the opportunity to inspect the old throttle body to see how the throttle position sensor is read. Looks like its an encoder wheel with hall effect sensors (see pic). I also noticed quite a bit of grease and debris inside the encoder/motor housing. More than I would have thought. Perhaps some of this is interferening with the encoder? Who knows. Anyway, thought I'd document things here. I'm not the only one with this issue. Should this not solve the problem, only thing left is wiring harness and ECU. I doubt its the later, as the car runs great for a few days, then throws the code. I've gone through the wiring diagrams in the workshop manual, and identified all the plugs and wire locations in the event I have to head in the direction. The harness side of this is pretty simple, actually, with only one intermediate plug in the whole chain between pedal, throttle body, and ECU. All FYI, YMMV.

pics:
1) replacement (used) throttle body off eBay
2) old (broken?) throttle body
3) interior of old throttle body showing throttle plate position encoder.

 

Car threw the P2127 code again today. At this point I've:

replaced the battery
replaced the pedal assembly
replaced the throttle body
verified conductivity on the wiring harness pins via my multimeter (took hours deciphering the wiring diagrams to do this, BTW)
unplug/replugged every connector in the chain multiple times.

The only thing left is the ECU. I've got an appointment with the Jag dealer on Monday to reflash my ECU, and I've ordered a spare ECU and gotten in touch with a cloning service to copy over my unit. I'll update on progress.

I should note, there's a couple of stories on the Jag forums of others having this precise issue (P2127 code) and never finding the problem. In at least one case EVERY component in the chain, including harness and ECU was replaced, and still this occurred. Perhaps this is some kind of bug in the ECU (Bosch Motronic) software? Of all the cases I've read about, they've been on cars at least 5 years old. My hail-Mary is to reflash in the ECU to the latest software with the hope that this might have been addressed. I'm open to other thoughts on how to address this. Given that when the car goes into Limp mode instantly when this code is thrown, it's a clear safety hazard, perhaps I should file an NTSB complaint as well. Thanks.

 

One symptom that I've been thinking over is the the code throws the instant I turn on the car. As soon as I press the start button, the warning triangle and "restricted performance" shows on the gauge cluster. Given that on startup, the electrical system can spike (charing various capacitors, etc.), I'm wondering if this voltage drop is the cause of the code? There's a voltage regulator in the trunk who's job is to hold voltage on key components during auto start/stop. Anyway, used voltage regulator are all over eBay for very cheap. I've ordered one up, we'll see if that helps...

And another possible conclusion. As my code throws only on startup, and not when running, I don't think this is a wiring harness or connector problem. Other's have had issues in various conditions like left turns. After clearing the code, the car runs fine for a few hours or days, then throws it again on startup. This doesn't sound like a flakey connector to me, but who knows?

 

Did a bit more sleuthing on this problem. Having replaced everything but the ECU and the wiring harness, it's got to be one of those 2 things.

A couple of more bits of data. I read out all the live codes on my OBD reader, and noted something interesting: the throttle plate is listed as circuit "B" and there's 2 entries for the pedal position liisted as circuits D and E. Recall my error was circuit E. For this reason, I'm concentrating on the pedal-side of the harness. I had replaced both the pedal and installed a pedal commander box, and neither of these things fixed the problem. So, it's must be somewhere between the pedal and the ECU, if not the ECU itself.

I have the wiring diagram and color codes for all 6 wires which go to the pedal assembly. It's a redudant circuit in which each sensor in the pedal has a 5V feed, ground, and signal. The ground and signal wires are a twisted pair. I traced the wiring harness, and found the pedal-side goes through a cable connector in the driver's left-side footwell (labelled as C31C and C31D in the diagram, below). Inspecting this connector, and the wires were VERY tight and strained. So strained, I couldn't unplug it. The accelerator goes through pins 1-6 of this connector. The 5V feed for circuit E was extremely stressed, pulling on the plug. I remounted this plug, and cleaned the contacts, remounted plug shown below. And, so far, no codes. It's only been a day or two, but this is now the longest I've gone in a couple of days with no codes. We'll see.

My next steps will be 1) reflashing the ECU at the dealer. Then, if needed, I bought a spare ECU and will have that cloned. A final step should neither of these work is to try running the "D" circuit 5V power supply to the "E" circuit sensor. I'll post regular updates. Such a frustrating problem, and absolutely killer to the car. It won't run when this code is thrown. Thought it a good idea to continue documenting this here, in the unlucky event some other poor owner goes through the same problem. FYI.

 

Fingers crossed that your plug remediation did the trick!

 

Yeah! I believe the problem has been found and resolved. It's been a full week, and the car has been flawless. No codes, no limp mode, no issues. After 3 months chasing this problem, I've got it fixed. A couple of comments.

1) I replaced nearly everything possible in the throttle circuit: battery, accelerator pedal, throttle body, air filters. The only things remaining were wiring and the ECU.

2) reading out all the parameters on my OBD reader gave me a critical clue: the accelerator pedal circuits were labelled "D" and "E" and the throttle body was labelled "B". This helped isolate the problem to the pedal-side of the ECU (recall, my code mentioned circuit "E"). I did this late in the process, and could probably have saved myself the headache of replacing the throttle body had I done this sooner.

3) Installing a pedal commander box was helpful. It isolated the problem to between the box and the ECU. In other words, it was either the ECU or the wiring. And, the pedal commander is awesome. Seat-of-the-pants feel of the car is totally changed for the better.

4) Approaching this issue methodically enabled me to finally isolate the problem to a plug that had a bad connection. This plug wasn't anywhere near the other components. The wiring diagrams and plug-quick-reference chart were essential here to finding the location.

5) A more general observation is our cars have hundreds of plugs and the connection CAN go bad. I think many of the intermettant problems reported may be due to this issue. The lesson here is the wiring diagrams are your friend. If you get a similar problem, look for common plugs in the wiring diagram and inspect/clean as necessary. Clearly, these connections/plugs can go bad over time, as mine did.

Excuse the long thread here. My 3-month adventure is resolved. I have a box of spare parts to show for it, and the satisfaction of fixxing it myself without much more cost. Finally, the title of my thread is now correct.