Hey All,

Got a funny issue with my '01 XJR with 82k on it that comes and goes, seemingly at will. I've researched some of the more common issues for the transmission and I can't make heads or tails of the issues that I'm seeing. I'm curious if it's something totally unrelated that this is an odd side effect.

• A couple months ago I'd felt a weird 1-2 shift where it surged a few times coming into the shift point. 2-3 was a bigger surge, maybe a couple hundred RPM, though enough to make it obvious. Going around a corner later that day, it felt like a torque converter clutch not engaging properly and the 'transmission fault' light came on. Pull into a parking lot, turn it off and on again, and voila - problem gone. I've had the same torque converter feeling come up two other times in the last couple months.
• I was getting on the expressway a couple weeks ago and punched it coming out of the corner onto the entrance ramp - the nothing happened. It seemed like the transmission was completely disengaged from any gear. Pull over, shut it off and turn it on again and it resumed like nothing happened.
• Then there was the one time about a month ago when I was pulling into a parking space - I went to put it in reverse (as I back in all the time) and it seemed as if the shifter cable was not even connected - it wouldn't engage reverse, then wouldn't engage any forward gear. Shut it off, turn it on, and again it resumed like nothing had happened.

It seems to be electronics related, and I'm not quite able to pinpoint what it may be. Maybe 10 months ago I started having some issues with the brake switch needing to be adjusted or replaced due to the engine failsafe mode/ brake light malfunction issues - I'd removed, cleaned and adjusted the microswitches and the problems had vanished. I'm not sure if what I'm seeing is an odd side effect? I do have the switch to replace, just in case. I am curious, though, about what the charging voltage should be when at idle. I'm wondering if a low battery might be the culprit as it occasionally takes a couple seconds to crank over. The battery is 14 months old and was new in the car when I bought it. I'd seen as low as 14.04v at the battery terminals when idling, and it seems a bit low to me. Might this be a sign of an alternator on its' way out? Serpentine belt stretching? I don't believe it to be an issue with the shifter cable stretching, though anything is possible.

Has anyone had similar symptoms? If so, I'd appreciate your feedback!

 

Did you already try adjusting the shifter cable? Was there any obd2 codes logged after the transmission fault error?

 

@nilanium I've not been able to pull any codes at all (I'm using the i930 unit). I have not done any adjustments to the shift cable yet, though will plan to try this in a couple days.

 

13 pin connector is probably leaking

time for a full trans service anyway

 

New batteries are junk these days

13.5 volts with a running alternator is the lower limit , the standard place to measure is the B + post on the alternator as there are variables on the way to the battery post

You have 2 throttle position sensors on the V8

one for the engine ECU and one for the transmission ECU

Both ECU's must coordinate with each other

There have been history of fluids leaking into the on the transmission body connector from above

There are 2 sensitive transmission input and output speed sensor wire paths through it to the transmission ECU

 

I had very similar symptoms with my XJR when the transmission needed to be serviced. I didn't realize it, but fluid had been slowly leaking from a crack in the transmission plug adapter and the fluid level had gotten low. I ordered a transmission dipstick for about $9 on Amazon and used it to add the proper amount of fluid. After adding fluid, all the symptoms went away. I drove the car for a couple days without any symptoms before taking it to my mechanic to have the transmission serviced and plug adapter replaced.

 

@Parker 2 - Interesting that you mention two TPS sensors, definitely something worth checking out. If I pop off the connectors, should the resistance be the same for both sensors?

@xalty @Parker 2 - You both might be onto something with the connector - I'll have to check into how to access it to verify.

@brian2891 - Was your transmission physically leaking that you could see? The only thing that I've seen leak on this car was some seal on the engine when it gets cold out (I'd seen the same exact thing on my '03 under similar conditions and wasn't concerned about it).

 

See page 59 lower right corner for TPS 1 and TPS 2

http://www.jagrepair.com/images/Auto.../jagxj2001.pdf

The 2 TPS sensors will be close but not exact as you very slowly open the throttle butterfly

You should not see a spike to zero volts

The output signal should be 0.50 volts dc at the idle stop on wire brown and wire green ( the middle 2 wires on the connector that has to remain connected )

You can do this test with the engine not running but the key in the run position

 

I had a similar issue some years ago. I changed the ATF and new conductive plate (with plug) and replaced the shifter assemble.

the problem never came back.

 

@brian2891 - Was your transmission physically leaking that you could see? The only thing that I've seen leak on this car was some seal on the engine when it gets cold out (I'd seen the same exact thing on my '03 under similar conditions and wasn't concerned about it).[/QUOTE]

No, I didn't see the leak and never found any indication of a leak on my garage floor, so I was very surprised to find that the transmission fluid was very low!

 

New plug, filter, ATF and trans mount cured my rough shift issues. Did it at 70K, still running smooth at 98K.

 

Appreciate everyone's feedback here! I'd ended up picking up one of the dipsticks from eBay (turned out to be a piece of trash - rubber end that curled around when it hit the pan), marked the hash marks on a piece of solid core copper wire, saw that I was a bit low on fluid. Quick trip over to the local Merc dealer and they had me squared away for around $160 out the door for the fluid, filter, seal, connector and locking pin. I usually source parts from Terry's Jag as they're reasonable and have great service, but $115 for the filter, seal and pin was too much. The car is shifting perfectly again and very happy I took the time to do the trans job.