I have a 2002 XK8 with 160,000km on it that started throwing the GEARBOX FAULT" message on cold start ups only.
Code P1747, pressure regulator 3, open or shorted.
A restart generally cleared it, but over the course of a month or so it now happens 90% of the time.
With the "GEARBOX FAULT" message displayed it jerks hard going into reverse only, forward gears engage normally.

Battery is new, voltage is good, 12.8, and it is on a battery tender when not being driven.

Code list when the fault occurs
1. ECM - P1747 2/4 Brake timing solenoid circuit malfunction
2. TCM - Transmission control module- P1747 Pressure regulator 3 malfunction
3. IPK - Instrument pack U1261 SCP (J1850) (-) circuit failure
4. DSM - Driver's seat module U1135 Ignition status not obtained
5. SLM - Security locking module U1135 Ignition status not obtained, U1041 Vehicle speed not obtained, B24BD Diagnostic trouble code invalid
6. PDM - Passenger's door module B2323 Driver's mirror horizontal feedback potentiometer low, B2327 Driver's mirror vertical feedback potentiometer low, U1041 No description available
7. DDM - Driver's door module B1402 Local door window glass circuit failure, B2182 Remote door window glass, B2336 Mirror switch assembly - circuit failure.
8. ARM - Restraints control module B1869 Air bag warning lamp - open circuit.
BPM is missing from report erratically, but seems to function correctly

After clearing codes and restarting without an error message the top 3 codes are gone.
1. ECM - P1747 2/4 Brake timing solenoid circuit malfunction
2. TCM - Transmission control module- P1747 Pressure regulator 3 malfunction
3. IPK - Instrument pack U1261 SCP (J1850) (-) circuit failure

I tested the resistance of the pressure regulator at the TCM connection and it was good, approx 6.5 ohms.
I have removed the transmission pan and filter, tested all the wiring and solenoids/pressure valves and internal wiring harness.
Everything tests out fine. The wiring connectios are slightly different than earlier years. I figured that out testing the internal harness.

I have removed every module but the door modules, they are next, and cleaned checked connections and internal boards for corrosion.
No "bad" connections found so far, mild corrosion that cleaned up well on a couple of boards.

I am working under the assumption that the transmission is fine and the issue is electrical.
The transmission works geeat when the code does not appear and simply cycling the ignition on and off with starting the car sometimes clears the GEARBOX FAULT message.

I have a ton of hours into troubleshooting this with no luck.

Any ideas?

 

I would concentrate on pressure regulator number 3.

I had a persistent P1745 (PR #1) on my 2000MY sedan and finally replaced the PR with a good-used part from another gearbox.
PROBLEM SOLVED.

 

Hi Gene,

In addition to Bob's good advice, there are pinpoint tests in the Workshop Manual that give instructions for testing the pressure regulator and its wiring with an ohmmeter. Bob kindly provided the pdf to Jaguar Forums and you can download it here:

Jaguar X100 Workshop Manual - Second Edition 1999 - 2002

You can download the 5HP24 DTC Summaries manual at this link, also courtesy of Bob and our member Gus, who hosts the file on his website:

Jaguar ZF 5HP24 DTC Summaries

On our X308 with the same ZF 5HP24 transmission, I chased a persistent P1748 Pressure Regulator 5 code for a few years. I followed all the pinpoint tests and even replaced pressure regulator 5 and the transmission internal harness, with no success.

I finally decided to try replacing the TCM and found a used one with the same part number and VCATS verson on ebay. The first one I received resolved the P1748, but it had a persistent P1726 code, so I knew I was on the right track. I found a second used TCM on ebay, and that finally resolved the codes.

Since a used TCM can be purchased for around $50.00, one way to approach your issue would be to perform the initial pinpoint tests for resistance at the TCM connector pins, and if the resistance for PR3 is within range, try replacing the TCM before you crawl under the vehicle to test resistances at the Mechatronic connector and potentially drop the transmission pan to replace the PR or internal harness.

Cheers,

Don

 

Thanks for the advice guys.
I've gone over all the pin to pin measurements.
One more time, then I guess it's time to start swapping parts.

 

My continuity/resistance tests on the PR #1 was very close to the other PRs measured at the TCM connector so the entire harness was included in the tests.

Only a slight difference in resistance but apparently enough for the TCM to flag the fault.

 

I'm dreading opening the pan again, I made a hell of mess!

I first noticed the issue when the engine was cold.
After the first error I wouldn't get it again all day, next morning, same thing.

That might indicate that the PR was faulting with the thicker cold fluid and squeaking by once it warmed up a little?

When I was searching the various forums for tips I noticed that the vast majority of PR faults are #3, more than all others combined I believe.
Makes me wonder if it is used more often than any other and it simply wears out, although solutions for the P1747 code vary from a bad ground to a new transmission though so that doesn't really work.

I've had my XK8 for 2 years now and there is no way it would be on the road without this forum.
I really appreciate all the help you guys offer!

 

I remember looking at the electrical guide and measuring all the PRs resistance to look for variations in the resistance of all the other PRs.
The one faulted (#1) was a few tenths of an Ohm higher resistance. OUT OF TOLERANCE was enough to set the DTC every few days.

I don't know the parameter deviation to set the DTC but it is not much.

I learned that the older PRs with BLACK ends vs the ones with colored ends should not be mixed.(I think the # 1 was GREEN in the faulty gearbox)
The black end PR flagged the DTC again when I replaced the green one.

I also tried different TCMs but my issue was definitely the PR because when I replaced it with a similar GREEN colored the problem was GONE.

Just replace LIKE FOR LIKE when the row of regulator/solenoid/actuators are concerned.

The ZF5HP24 differences seem to be UP TO 1999 and FROM 2000 ONWARD (F00001 or A00001 ONWARD)

Solenoids are different.

ENTIRE gearboxes seem compatible. (keep all regulator/solenoid/actuators as a group?)

 

That was exactly the symptom on our X308 and your thoughts echo my own regarding performance of the PR with cold fluid. But in my case, replacing PR5 and the internal transmission harness made no difference.

I thought I was on to the root cause when I measured the old internal harness and the new salvaged harness and found the wiring for PR5 in the old harness had 2 or 3 tenths of an ohm higher resistance than the PR5 wiring in the new harness. But replacing those components did not resolve the P1748. This was one of the few times when I have had to replace a Jaguar ECU to resolve a problem, though I have had to repair many modules, especially the ATE ABS modules.

I suggested that you try a different TCM first simply because it is so easy and inexpensive compared to the inconvenience and mess of dropping the pan. I know it violates all of the rules we try to follow about following the diagnostic flowchart until you're certain of the cause, and only then replacing a part. But once in awhile it's worth trying a shortcut.

Cheers,

Don

 

It's definitely time for a short cut, the last of my hair is falling out

I found a tcm online for $50 so I ordered it.
It seems like no one tracks vcats info on modules so its a crap shoot, but it might help troubleshoot if it doesn't solve actually the problem.

The attached pdf shows the transmission solenoid activation conditions.
It might explain why PR3 seems to be the one that goes bad first.

 

Here's a photo I took of a TCM and I have outlined the part number and VCATS version in red. The part number of this one is LJE 2401 AB, and the VCATS version is 002. From what I have been able to determine, during the X100/X308 era, the VCATS versions were 001, 002 and 003. If you match the TCM part number and VCATS version, you should have no issues.



Cheers,

Don

 

That's great information. Everything I've read said there was no vcats info on the modules themselves.
Mine is /003 and the label on my module is 003.
The pic was for a 002, I'll have to see what they actually send, maybe I'll get lucky lol

 

GENERALLY there is no info printed on the module but sometimes you get lucky!

The parts dept was ALWAYS needing the VCATS and there is a provision to decipher if the module is in the car with network intact using WDS/IDS.

The boot label is the key so I ALWAYS record ALL my vehicle modules and document them.

Take a pic or write them down.