&$&#ing PO836 returns...

[nudibranches]

So after a year of trying to fix this rotten issue it keeps coming back.

To date I have replaced the TC sensor switch (twice), both genuine MOPAR and the last one has been tested and is okay. (These are not DORMAR or third party, they are genuine MOPAR from authorised seller).

Replaced the wiring from the sensor to the ECU, totally new wiring.

New DELPHI connector.

Checked the TCM just in case, even though this shouldn't produce any
P0836 issues.

Into the bargain checked the wiring into the mechatronic plug into the tranny. Again all okay.

And...still get the code and the tranny does weird things. It does not go into limp but the MIL light will sometimes come on for a short while and the tranny will skip a bit (P0702).

Codes, usual P0836, P0702 and P240D-ID44-Engine T-Case; no one seems to understand definitely what this last one is.

I know some guys (Jean Luke) have placed resistors at the TC sensor side and this seems to have solved their "problem", even though this is presumably masking the issue?

From what I can tell the P240D-ID44-Engine T-Case code seems to change the shifting strategy and sometimes I will get this code and second will take a little longer to shift, but no MIL light and no PO836. I can live with that as it only happens intermittently.

But then the PO836 comes on and throws the MIL light. I am of course in mortal fear that the next time it comes on I will be in LIMP mode 80km down a bush track. That said, it hasn't gone into limp as mentioned earlier.

There must be a resistance issue as these jeeps get older? Although it doesn't happen when the engine is particularly hot, not that it ever goes over 100C, even when churning up a long steep hill...as per Clyde River mountain pass this morning. Engine was fine and smooth. The PO836 came on when we were cruising along at 100km on the flat and the engine was at 88C. The MIL light came on and off (only a few seconds each time) about a dozen times over an hour or so and then stopped.

I've checked the volts at the sensor via wjdiapro and they are stable at 1.465 but then oscillate to 1.480 frequently, but as mentioned genuine switch and completely new wiring and connector.

So....one last throw of the dice on this and then I'm seriously considering vacating WJ ownership as these cars just become more and more problematic as they age. Like all of us.

[Grippy]

Is this diesel or petrol?
I was always paranoid at the end with my WJ, I carried a heap of different sensors I'd picked up, although changing some of them in the bush would be a ball ache.

[nudibranches]

Diesel. If, as I suspect, I punt the WJ the next car will be petrol and manual.

[bodgie]

I'm wondering if it's an electrical noise rather than a resistance-related thing?

When you rewired the switch to the ECU did you disconnect the old wiring? Have you compared the old switch to the new switch to see if they measure the same?

Tried putting the old switch back in?

I feel you about buying a petrol car for my next one too but everything has its issues.

Jason

[Adrian D]

What about ground points and ground straps? Are they all in good condition?

[nudibranches]

Bodgie and Adrian,

yep, various things and all you have outlined have been done over the past year. The problem just keeps coming back.

After spending a LOT of time over the past 12 months researching this, it seems most people end up changing switches, wires etc but the problem keeps hanging around. So they end up whacking on resistors to try and mask it.

This might be something a flash fixes, but I doubt Jeep has a fix for an 18 year old car.

As mentioned, they don't age gracefully in this regard.

And yes all cars have potential problems, but I'd gladly swap this for a petrol/manual as at least you have eliminated these type of wiring gremlins.

Albeit invited a different set into your life.....

[Jonny Jeep]

It seems Mercedes transmission can have an issue with TC position and it's often due to a bad ground.

I'd start by checking the resistances of the 4WD position sensor with the TC in the different drive modes and compare those to the chart I posted in one of your other threads.
Then, plug the sensor in and compare those readings to readings made at the engine control module C1 connector between pin 21 - black/light blue wire (sensor ground) and pin 29 - brown/white wire (TC position sense).

If the wiring is good, the resistances would be no more than a few ohms different to those measured directly at the sensor. If they are much greater, tap the black/light blue wire near the sensor and run a wire to a good ground and check the readings at the engine control motor again.