Hi,
I'm new here and I have a '00 XJ Executive 3.2. For quite some time, the CEL has been coming up occasionally, likely due to yet-to-be-found leak in the exhaust manifold. Lately, after coming from the shop where it spent about two months while they were trying to fix the exhaust leak (which they failed at) and rebuild the front suspension (which they did a good job on), either Gearbox Fault or Restricted Performance started coming up, both typically when accelerating over 80 mph uphill on the highway.
Later, both problems started to appear more at random, twice going as far as to stop the car (after 15 minutes, it fires right back up and everything seems fine).
A friend of mine who ran the diagnostics says it's likely a combination of dead mechatronics on the gearbox and the timing chain "jumped a tooth". I don't remember the error codes, but when hooked on the diagnostics, a lot of values seemed to be totally off – as in negative temperatures, maybe even some negative volatege.
Is it possible that it might be some electric gremlin and not a transmission + timing gear (which would cause me to sell the thing for peanuts and look for a better one)? For a long time, I used 72 Ah battery, which I learned might be a problem, now it's got a nearly brand-new 100 Ah one.
I've heard about electric problems causing stuff like this – there were apparently some problems around the battery, could it be something as easy as wiring issue?

 

00 XJ Executive 3.2 was not offered in North America so I am not too familiar.

I assume it also uses ZF transmission.

on the R model, it uses the Benz 722.6 and the faculty electronic conduct plate is the usual root cause.

 

It is mostly the same as the 4.0, same gearbox and mostly the same electronics I think. I think it lacks VVT and something like that, but generally, it should work like the four-liter.

 

Don't know, if this helps, but when I bought my 1998 X308 XJ8 3.2L it came with "restricted performance". Obviously that could have had many reason - but I found the reason for mine (with a scanner) quite quickly: It needed a new knock-sensor. I found them cheap on aliexpress and this was an easy fix.

 

The ZF 5HP24 does NOT have a 'mechatronics'.
The gearbox uses a TCM mount in the 'cool-box' that also houses the ECM.

 

The guy doing the diagnostics might have used wrong term, or I might've used wrong translation – we're both from Czech Republic.

Anyway, he says that it is most likely a mechanical problem that would lead to replacement of both timing gear and gearbox. I still suspect that since when the car runs without error messages, it runs totally fine (shifting, power, everything like it should be), it might be some electric gremlin somewhere.

It seems worthwhile to keep looking for the gremlin for a bit than just jump on spending the price of the car on gearbox and timing gear (which would probably mean that I would just buy another car).

Any ideas?

 

The camshaft timing is quite easy to check - remove the cam covers and check whether the flats on the cams align (if you are not clear as to how this is done, check the manual or this forum about the procedure).

These cars are notorious for giving you many false warnings if the car's system voltage drops for some reason. I once had "Gearbox Temperature High" and "Restricted Performance" when my alternator was on the way out and the voltage dropped. All I had to do was fix the alternator. So, I suggest you first check the alternator voltage while driving (use a cigarette lighter voltmeter), inspect/clean all contacts of the battery cables including the connections on the master fuses in the boot and the connections of the main supply cables at the false bulkhead and at the fuse boxes.

 

There seems to be a history of the on the transmission connector getting oil in it

There are 2 speed sensors in the transmission that communicate to the transmission ECM which in turn cross talks with the engine ECM as they coordinate their dance together

The connector if the same as the earlier 4 speed ZF version does not simply twist off but first be moved aft about 1 / 8 inch to unlock and only then twist off

Large tiewraps on the connector help grip to twist off

ZF5HP22 or 24 ? data plate on right side

There is also