Transmission overheat p1793

[wpoll]

Originally Posted by andrewwynn

...

The order times was from water getting into the main transmission connector on the back of the transmission.

Not a lot of rain in Queensland right now...

Also, our diesels have a large plastic under shield that covers the entire transmission and transfer case, making it pretty unlikely that water can get up there. Never say never though...

It sounds rather odd that the error pops right back when cleared, without a run. Perhaps it's not clearing correctly? What scanner are you using again?

Are there any other symptoms beyond just this error code? It trans still in limp mode?

[andrewwynn]

I think the water works its way down though the wiring harness from under the cabin air filter. It may take weeks or longer to seep down though the cable.

When I first had the water intrusion problem there was no rain anywhere near the ocxurance and the "comes back without driving" also happened.

On foxwell it will show realtime the L1 (I think that's what they are called) signals from the gear selector switch. If they don't snap to the correct value during gear change nearly 100% chance you've got water in there.

[wpoll]

Originally Posted by andrewwynn

I think the water works its way down though the wiring harness from under the cabin air filter. It may take weeks or longer to seep down though the cable.

...

I guess that's possible, although I think Gixman05 has the same ZF 6HP26X transmission as I have and the transmission harness is at the front of the transmission, up high. Not like the GM 5L40-E, where it is low and at the rear... I'm not sure I've heard of anyone having water ingress issues on a ZH 6HP26...

But if it did get in there, heck yeah, all sorts of issues could ensue...

Does the ZF 6HP26X have a temp monitoring diode in the wiring somewhere? If so, does it fail occasionally... ?

Something I'll look up some more on tomorrow...

[andrewwynn]

i believe the temp sensor is in the wiring harness right inside the transmission. there is no reason to expect that won't fail some times and give you an overheat indication which would surely kick in failsafe. a decent scanner or app will give you realtime temp of the transmission to determine if the sensor is reading correctly; does it match ambient after car has not been running?

[andrewwynn]

Originally Posted by wpoll

I guess that's possible, although I think Gixman05 has the same ZF 6HP26X transmission as I have and the transmission harness is at the front of the transmission, up high. Not like the GM 5L40-E, where it is low and at the rear... I'm not sure I've heard of anyone having water ingress issues on a ZH 6HP26...

my theory is the wather comes from the top and the front, meaning it would be more likely to be a problem on the ZH than the GM unless something about the harness on the GM causes it. I've chatted with about 3-4 people on xo that have had the same problem on both 6 and 8 cyl. gas, and no reason to expect it couldn't also happen on the diesel.

I would absolutely check the transmission main harness plug first thing when i get any internal transmission error. I was quite panicked when my transmission started to slam shift 2>1 and more or less run like crap; now in my case, i noticed the PRNDL didn't light correctly, it actually said i was in 54th gear at one point but all 'the inter webs' pointed me to the problem was the gear selector switch (which is external in the 4.4 but INTERNAL on the 3.0) so i was dreading dealing with that until a member on xo mentioned he had similar issues until the dealer after a month of guessing opened up the connector and a bunch of rusty water poured out; same exact for me; cleaned all the contacts and put back together and reset the transmission error and it worked perfectly after.

[wpoll]

Originally Posted by andrewwynn

i believe the temp sensor is in the wiring harness right inside the transmission. ...

Yep - found an image... *edit* seems this image may be from a 5HP24.



Seems this could be a real over-temp scenario (blocked/failed trans cooler or blocked/failing radiator?) or just failed temp sensor. andrewwynn, your suggestion of monitoring the live temp values may be the only way to be sure.

*edit* rrphil provides some valuable info on this thread - including and alternative way to measure teh temp sensor (at least, in a ZF 5HP24).

https://www.rangerovers.net/threads/...rature.215778/

I'm still wondering about how the code comes back so fast though - that bit makes no sense.

[andrewwynn]

actually makes plenty of sense; if the thermistor is broken and reporting 500F for example, you can clear the code but it will immediately return because the transmission is 500F as far as the computer is concerned.

FYI; this could happen from rusty water in the connector. I had similar issues but the DME was convinced I had both 4th and 5th gears selected at the same time for example. (because some of the pins were shorted); now if the pins to the thermistor are shorted, you can get either off scale high or off scale low temperatures.

Now it would be *nicer* if the DME would report an error 'implausible temp' vs 'over' temp.

If you pull up realtime temp of the transmission (foxwell 520 will do this), it should show ambient temp initially; if it shows *anything* else it's erroneous data and needs to be investigated.

I've come across at least one case online where the thermistor went bad and replacing the inner cable was the repair required, but can't remember if that was an x5 even, just that it's been in front of my eyes before.

[wpoll]

Turns out the 6HP26 temp sensor is a TFT built into the mechatronic assembly...



... along with the ISS and OSS. Not so easy to replace.

So yeah, as andrewwynn suggests, start with checking the connector!

[Gixman05]

Wow awesome info and a few good places to start. I did pull the plug and was fairly clean.i was thinking temp sensor or burnt broken wiring as it seems to have happened while the car was stationary and hasn't been driven for about 7 days. I will check the real time temp when i get back to my car thx again

[Gixman05]

transmission temp is 26deg Celsius which is about the same as ambient temp. cleaned the plug did seem to have some oil in there so possibly could have caused an issue. will throw the pan back on and fill with oil and see if the fault persists.also my park light, low beam and tail lights check comes up on my dash now as well, they are working so either another isolated issue or it could be connected who knows.