Facelift Transmission Problem P0758

Had an issue with the 1996 XJS transmission…. The transmission light came on and I was stuck in 3rd gear. I pulled over, turned the car off/on and light with issue was gone. I was hoping it was just a weird random occurrence.

On my way home, it happened again. This time on the highway. No big deal, was able to get it home and pull the code.

P0758 - something about transmission shifter solenoid B

I went through my records, and although the fluid seemed red, it turns out the fluid is 7 years old and has over 60,000 miles on it. Yikes!

I sent it to the shop to get the fluid flushed. Hopefully that solves the problem. When I dropped it off, I got a check engine light, with the following code.

P1775 - No data exchange between ECM and TCM because of internal fault in the switch


Faulty Crank sensor

Im assuming it’s the first one.

Anyone have any experience with this. I went through the forums, but I didn’t find much. I found a few posts that replaced the solenoid, the TCM, neither resolving the problem. I also found someone replaced the transmission module harness, but no one ever came back to confirm success/defeat. I hate when that happens.

The P0758 is a gear ratio error code; the trans software is seeing a ratio of input vs output speed that doesn’t correlate to a gear. If you have a CPS code also, address that first, as the trans software might use engine rpm as an input.

CPS Code? I’m not sure what that is.

Thanks for the response.

EDIT: oh, you mean crank position sensor code. I don’t think it’s that. It seems to cover both, but I think it’s related to the transmission issue. We’ll see.

Crankshaft Position Sensor = CPS. Look at that and the P1775 first.

My ‘99 XJR had a similar named fault and it was the turbine speed input signal or some such. On the Merc box of course this meant a strip down of the solenoid area, other vehicles have access from the side of the box :imp:

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It’s only been one drive, but the transmission fluid replacement seems to have done the trick. Will report back if anything changes, probably will not report back if the code does not return.

Car is back from transmission specialist. They didn’t charge me much because they didn’t find the problem. They tested solenoid b and it tested good. They recommended swapping out the transmission ECU.

I bought an ECU and same problem….so it’s gonna be a wiring/connection issue?

I trust the tranny shop. So the solenoid doesn’t need to be replaced.

I swapped out the ECU, so that gets crossed off the list.

Am I simply taking ohm readings from the connector at the transmission and the ECU?

Should I make plans to replace the plug at the transmission?

Is there anywhere else I should be looking at?

I noticed that the XJS used the same ZF 4HP24 transmission for MYs 1989-1996 for the non v12 engines.

Would anyone know if the harness changed for the different model years? I’m having trouble finding one.

Looking up the wiring diagram, it does reveal that the connector is a 9-way Hellerman Deutsch connector….now to find which one.

Pulled the connector at the transmission…its wet with transmission fluid. I flushed it with contact cleaner spray.

I also checked the continuity between Solenoid 2 pin K and the corresponding Pin 24 on the transmission ECU harness. I got an ohm reading of about 0.75. I stuck a common nail in both female harnesses and then connected them with alligator clips and 16 awg wire.

I’m gonna take continuity readings for the remaining pins at the tranny harness and rub in some Lubrimatic Electrical Contact Grease (not dielectric grease) and see what happens?

Any suggestions while I’m doing this?

So….I checked continuity on all pins. Everything checked out.

I cleaned the connector, and greased the pins.

Tightened up the somewhat loose male connector with a 30mm socket.

Reconnected it, and took a spin around the block….no change.

Not sure what I can check next.

When you stated you pulled the connector at the transmission, did you mean that you only unplugged the connector, and you found transmission fluid in there? I am thinking that you will have to remove the connector, that is mounted in the transmission body - possibly it is cracked and allowing fluid to cause a short between pin terminals - may have to place catch pan for fluid loss when removing connector.

Thanks for your help. Yes. I did have fluid inside the connection! Your theory is helpful!!!

I have attached a photo of what it looked like before I touched anything. Note the drop at the bottom of the connector ring.

You can see fluid all over the place, then the two pics in my earlier post showed what it looked like as soon as I pulled it. I hadn’t done anything to it.


Here’s what the controller with the male connector connected to the transmission looks like.

I doesn’t appear that inside harness comes separately, although I am missing a washer.

When I checked the pins using the ohm setting on my multimeter, should I have checked all the other (relevant) pins while there?

For instance, when I had a probe tacked on to the solenoid 2 connector “K” at the transmission harness, once I confirmed continuity at the transmission ECU harness position “24”, I should have checked the other relevant positions? (38, 6, 46, 2, 5, 44, 42 and 19). Isn’t that the way to check for shorts?

I don’t think there’s any point to checking continuity at pins. There’s not supposed to be any ATF in the connector. You should address that problem first. Unfortunately, it probably means replacing the connector on the tranny, and that might in turn involve some serious disassembly.

Used to be a common issue on some ZF-equipped Chrysler products, and it could cause electrical faults that would trigger MIL illumination or default/limp mode. I would replace the bulkhead connector- if not available from Jaguar, perhaps one of the other users of that series of ZF transmissions.

Bulkhead connector is the nine pin harness attached to the transmission?

I checked it to make sure that something didn’t happen to the wire communicating to the tranny ECU.

It appears that the washer is missing at the transmission plug. I’m assuming that the tranny shop misplaced it. Maybe it’s a new issue due to the recent tranny shop. I’ll have to order one of those, thankfully available.

Cleaning it out and packing it in with grease did nothing. Not even momentarily. If that was the problem, I should have seen at least a short term correction.

No, the connector that mounts through the trans case; the piece the harness attaches to. You will have to remove the pan to replace it, has wiring connections to the valve body solenoids on the inside. Should not have fluid inside the connector.