01 XJR with 169,000 miles. Had PPS problems with my original throttle body, finally bought the remanufacture service from ASI, ended up with a completely different TB off the shelf. Got it installed and all is well back in January/February of this year. I did get an engine failsafe mode issue right off the bat, ASI recommended doing another hard reset which seemed to address it. Fast forward to mid August and I go into failsafe mode again, this time with a MIL indicating code P1122 (TPS circuit intermittent low voltage). I pulled the connector, cleaned it with spray electrical contact cleaner and the TPS side, let it dry and reconnected, did a hard reset and all is well. Until Tuesday when it went into failsafe mode again. I pulled over, restarted, seemed ok, drove another 10-12 miles and it did it again with a MIL, which returned P1122 again. Did a hard reset and drove to work and then later drove home without further incident, but car is parked now and I'm using my backup until I figure it out.

I've contacted ASI for assistance, waiting on a return call.

I believe my car has had the TSB 303-58 applied to it, the car side connector looks to have gold colored connectors inside the plug and the covering for the wires is missing, so I'm guessing this has been done before I bought it.

Apart from a replacement TPS, are there things I should be looking into on the car side of things? Anything I can test or examine that might cause this issue? I never experienced this with the old throttle body, that thing's problems were all on the PPS...doesn't mean something new hasn't come up on the car side of things, just that it never happened before.

On the off chance that ASI can't (or won't) be of help here, can anyone recommend a decent replacement TPS? I believe the OEM Denso product is out of production now?

Thanks!

 

This from another thread in our forum:
" with the car off, simply step on the accelerator pedal multiple times, in effect,
operating the potentiometers in the tps throughout their full range. Most potentiometers
have as part of their variable resister set up a "wiper" type device to clear the contact
surface, so operating the pot throughout its entire range can clear corrosion or debris
that is interfering with contact of the variable resister."

 

Digging in a bit more and finding a listing of OBD codes, I see that P1122 may after all be the PPS, the code list says that the pin 4 may be problematic, so I will investigate that connector when I get home tonight and see. The TSB 303-58 doesn't seem to mention, but I wonder if this pigtail is subject to the same issues as the TPS pigtail with dissimilar metal issues? If so, where does one go for a replacement end if its needed?

 

Randy, thanks for the info. I've give it a shot tonight as I'll be doing the PPS connector cleaning as well.

 

Disconnected the battery last night and left the negative cable end laying on top of the positive, disconnected the PPS connector and examined it. I completely forgot that the retaining clip broke off when I replaced the throttle body, but I had it ziptied on and the seemed pretty secure to me. None of the pins look questionable to me, all are gold colored, I see no abrasions on the wires so I think at least this connector is ok, minus the securing clip. I sprayed it and the PPS with contact cleaner and let them dry and worked a pick around inside each of the 4 connectors to scrape any contaminants off that I might reach, sprayed it again and reconnected it all. Left the battery disconnected overnight and later this evening I'll reconnect and try to recalibrate the throttle body and see how it goes.

Anyone know where I can locate a replacement connector? Photo attached.

In the meantime I have two emails and one phone message in to ASI without any replies from them in a couple days. Their phone system specifically states that all tech support must go through the website chat applet, however I could not find a chat link anywhere on any page, so I left a message with their customer service dept. Maybe I'll try calling sales instead, I bet they answer that line pretty promptly.

 

I had a similar problem with the PPS connector on my first 2000 VDP. I ended up cutting it off and soldering another one in its place which cured the trouble. In the meantime, I had gotten the TB serviced, installed a used TB, and replaced the TPS connector among other attempts. This went on over the course of a couple of years as it would work OK for a while then act up. It finally dawned on me it was the pedal position connector.

 

Recleaned and reconnected everything, nice shiny new zip tie on the PPS connector. Per ASI's instructions I connected the battery, powered the car on but didn't start it for 60 seconds to allow calibration to take place, then when I started it I got a rough idle initially, OBD reader showed me misfires in 3, 7 & 8, but it all smoothed out after about 30 seconds or so, no more misfires since then, these were accompanied by a code P1316, which also disappeared after driving. Unsure of what might have caused these to happen, but they all vanished on their own so I'm sure they'll never bother me again, right? RIGHT??

Couple days, about 200 miles so far and no hiccups. Still no word from ASI.

MIL came on when I initially started it, checked it after driving it those couple hundred miles, its showing a code P1647, which I believe indicates the upstream O2 sensor on the left side needs to be replaced. Bummer because they're spendy.

 

I am a firm believer that these cars were never meant to sit for long periods.
That is basically true for any and all cars but especially so Jaguars with all
the British designed electronic connections and the level of interdependency
that is evident.

 

Got the P1122 again on the way into work this morning. Happened twice today before I got to the parking lot. Contacted ASI again, hoping for a response. I'm frustrated with their lack of reply, but hoping they'll call me with a solution. If not I'll call their sales line, which I bet they answer.

 

A shot in the dark: any chance you have too much slack in the accelerator cable?

 

Its a possibility and I'll have to check it. When I got the throttle body I adjusted the cable to where it just barely had any slack at idle, but I think it hit 100% WOT before the pedal got to the kickdown switch. I did experience a couple restricted performance issues right off the bat, this I got a P1121, which was what prompted me to send mine in for refurb in the first place. I thought of the throttle cable at that time and backed the tension off a bit and the P1121 never returned. Maybe I have too much slack at idle now though, so I'll check my scanner's live data and see what % throttle I get when its floored and the kickdown switch is clicked.

Good idea, thanks!

 

@mayhem 100% can lead to restricted performance, being fly-by-wire throttle bodies it's one way to loose signal out of the sensors range.
When you recheck and set it next time, do it with kickdown depressed (WOT) set it as close to 99%.

 

Will do Sean, thanks!

I have been thinking its down on power lately. Even in sport mode it is impossible to power brake the rear tires with the throttle floored, at first I chalked it up to sticky tires and good brakes, but its just the regular base XJR rear brakes with brembo branded pads and rotors and I definitely have smoked the rear tires since I installed the brakes. It'll barely spin the tires from a dead stop and floored throttle. Maybe I'm nowhere near full power anymore.

 

Sigh.

Been working well for about 2 weeks and about 700 or so miles since I cleaned that PPS connector, though sometimes I feel like the throttle flutters a bit while I'm driving at a steady speed...might be me being overly sensitive or not. Last night it went into failsafe again after dropping my son off at his Mom's. Shut it off, restarted and finished my ride home without further incident. When it tripped into failsafe I was using cruise control, which I do use a lot. I'm not sure if cruise may or may not have a bearing on this issue.

Checked codes, sure enough P1122 again. Decided to check the throttle cable slack while I was plugged in. Connected my reader, turned the ignition on and started it connecting, which takes a minute or two. While it was connecting I pressed on the bit of throttle cable that goes from the adjuster bracket to the PPS itself, just checking for slack, which there is almost none. When I pressed on it, the PPS stopped making that telltale whining noise that it makes, which I thought was odd but didn't think much of it. Got my reader connected and loaded the live data, throttle was at 9.8%, fluctuating to 10.2% and then back, pedal does nothing. Took me a sec to realize the PPS is now off and that's why it stopped making sound earlier. Turned the car off and back on, PPS now laming noise and works ok. Idle setting is at 4.7%, floored pedal is 82.7%, WOT with kickdown switch is at 96.5%.

This morning I decided to chance it on driving to work, started the car and it started in failsafe mode, PPS making no sound. I let it run for about 30 seconds so it wouldn't bore wash on me and shut it off, took my truck to work.

It has to be either a bad PPS or something is cutting the voltage to it for a reason I don't understand. ASI continues to ignore me at this point. Am I missing something that anyone else has resolved? I can replace that PPS connector, but there's no way its not making a good connection I would think.

 

I would definitely look into getting a used TB. I know, I know…..

In the last 12 years of working on these cars, I’ve encountered maybe a handful at most where the PPS was at fault. The TPS, many of them.

 

ASI finally picked up the phone and said send the throttle body in and we'll repair it. I'll have to cover shipping in both directions. Fingers crossed...but this'll probably be a couple weeks before I'm back on the road.

This is why I keep a backup car though.