Hi everyone.
My X300 4.0 has lost drive, forward and reverse. I pulled away from junction with a bit of gusto and there was a funny sort of slipping belt noise and stopped moving. There are no warning lights on dash, have so far checked that the gear selector actually selects gears, both ends of cable are moving, reverse lights are working. The revs do change when selecting gear but nothing happens when try to drive away. Oil level is OK, oil is clean, no funny smells.
My question is, do I need a new gearbox? I'm OK with replacing it myself, just want to know if it's box or anything electrical.

Thanks
Tim

 

Hi,
Have you tried the S N switch and the 3 and 2 marked on the J gate?
John

 

Fuse for the transmission ECU

You should have the more advanced ZF4HP 24 transmission with electronic controlled shifting solenoids on the 4.0 non supercharged engine but the British market may have them mixed as factory equipment

Fuse # 14 / 10 amp left heelboard fuse box

Swap the left heelboard king relay that enables power to that fuse with the left engine bay king relay . The left engine king relay in reality only sounds the horn so there is your test

There is a screw head mechanical override on the top of the J gate in the following picture

 

What does the black box with red circle do?
John

 

That is the linear switch that gives you the " P " light as well as other things like what gear shift handle position selected commanded to the transmission ECU

There is a rotary switch on the transmission body that enables starter engagement

 

Hi John, yes there's no difference in either mode.

 

Have you checked the drivetrain?
The gearbox could be OK, and the problem further back, possibly Jurid coupling , Diff or driveshafts

 

This. No reverse and drive sounds awfully suspicious

 

Hi Tim,
This is a bit of a long shot, but have you asked the person you bought the car from if they have had the same problem?
John.

 

See page 50 of the doc below

On page 5 you will see the shift solenoids MV1, MV2 amd MV3 test resistance by reading the transmission ECU connector

All 3 should read about the same and best to change all 3 while you are there

 

Thanks for all your suggestions.
I have checked that the other bits are intact, the prop doesn't turn when any gears are selected.
I also checked the fuses and relays with no success. The previous owner obviously has had no such problem before.

 

Hi Tim,

Have you checked your transmission fluid level and for signs of a leak?

Have you connected a scan tool to check for any stored diagnostic trouble codes? If the problem is electrical or electronic, we would expect at least one or more DTCs to be flagged.

When you say that both ends of the gear selector cable are moving, is the lever on the side of the transmission moving through all of the positions of the rotary switch?

The 4HP24 transmission has been essentially bulletproof, but an internal mechanical issue is not impossible.

Cheers,

Don

 

These are the only fault codes I found. There are no warning lights on dash.

 

P0727 indicates that the engine speed signal is low. Possible causes include:

Engine stalled while driving
ECM to TCM engine speed signal circuit open circuit or short circuit to ground or B+ voltage
ECM engine speed signal error

See pdf page 122 of the transmission Service Training Manual I am attaching below.

The ECM engine speed signal originates with the Crankshaft Position Sensor (CKPS); if your CKPS was malfunctioning, the engine would not run. One possibility is that there is a problem with the wiring that transmits the engine speed signal from the ECM onward to the TCM. Another possibility is that this code was triggered by the engine stalling.

The engine speed signal is transmitted from the ECM to the TCM on the Purple wire with Yellow tracer line which connects to pin CC7-3 of the TCM connector. See pdf page 78 of the attached Electrical Guide. You can download the 1996 edition here (you haven't mentioned the model year of your car):

Jaguar X300 Electrical Guide 1996

The P1621 code is not defined in the Jaguar literature I have for the X300, and I have seen accounts that called it a red herring, or a false code with no meaning. It may be your scan tool's way of trying to parse a proprietary Jaguar code. I also found one reference that gave these definitions for Jaguar:


If these definitions are accurate for X300-era Jaguars, then they could be viewed as consistent with P0727 being flagged due to a problem with the engine speed signal circuit. It might be worth checking the connections at your ECM, check for water ingress, and clean the ground points referenced by the ECM (also shown in the Electrical Guide). You can test the continuity of the Purple/Yellow wire from the ECM to TCM with an ohmmeter, and also test for a short to ground or battery B+ voltage.

The P1621 DTC has also been associated with a failing ignition coil, but we would expect at least one misfire code if that were your issue, and I don't know if that could cause your transmission to fail to engage.

All that said, it is still possible that your CKPS is failing intermittently.

Please keep us informed.

Cheers,

Don

 

Thank you Don, that was extremely helpful. I shall check the wiring connectors and continuity. The codes were cleared and haven't returned but that's possibly due to the car not moving? The engine starts fine, no misfires, no MIL on.

 

The transmission has it;s own speed sensor other then the engine having it's own CKPS ( crankshaft position sensor which obtains both the crankshaft angle position and speed )

The engine CKPS will read as a basic reading of 1300 ohms , the functional reading is hard to see unless you have a oscilloscope

The transmission speed sensor would be of the same basic reading of not 1300 but 125 ohms

See page 63

The transmission ECU is a Bosch and the engine UCU is a X

In the early design days of OBD 2 and it's shortfalls this may be one of the things not nailed down as accurate ( just an opinion not based on fact )

The engine CKPS does have it's problems before it completely fails

The transmission speed sensor can be easily read from the transmission ECU connector at pin 2 and 38 while you read the 3 shift solenoids and you might as well read the pressure regulator as this may have a fluid open / close function along with the pressure regulation so things don't slam together

This open / close function of the pressure regulator may be the issue of your transmission not shifting ( or too low a pressure from a mechanically failed regulator )

 

My car is a 1995 MY.
Thanks for the information all.

Tim

 

Ask all the other forums of cars with the same transmission (Range Rover, BMW E32, etc) if they’ve ever heard of a 4HP24 able to shift between gears but unable to move at all.

 

Have you tried the manual over ride screw on the J - Gate light plate ?

I've never used it so some else would have to advise on it's use

 

The manual override just allows the gear shift lever to be moved out of Park in the event of failure of the interlock solenoid. Moving the gear shift lever out of Park does not appear to be Tim's problem.