45RFE Transmission limp mode when idling

[driconrikus]

Hi guys,

I have an '02 Jeep Liberty KJ with a problem in the transmission that only happens when idling in either park or neutral.

The weirdest part of this issue is that I can drive for hours and it will shift properly, until I stop and put it in either Park or Neutral then I put it back into Drive, it sets limp mode and only uses 3rd gear. The problem goes away when I turn it off and turn it back on then put it into Drive, I can drive for hours without it going into limp mode and it will go through all gears until I put it in park/neutral again.

If I stop but leave it in D in traffic lights for example then accelerate, it does a single jerk at 1st but applies all gears without issue.

The transmission has already been serviced, solenoids replaced, and changed oil. My mechanic dropped the transmission, tore it apart and did a visual inspection and there are no signs of mechanical failure, looked clean.

I have run a scanner and I get the following codes: P0841, P0868, P0841, P1775 when in Park, these codes go away when I turn off the engine and turn it back on and put it into Drive and come back on when I either put it in P or N.

This got me thinking it could be an electrical issue rather than mechanical. I have done a few multiple hour long trips without it failing and I also drive it daily, if I stop I just restart the car and shifts normally. Will I damage my transmission if I keep doing this workaround?

What I'm planning to do next:
- Replace the transmission fluid sensor
- Replace transmission filter.
- Reprogram TCM

But I'm looking for more opinions, what do you think this could be?

 

[ikuo78]

In other words, if the range sensor detects P or N, the connection between the ECM and TCM will be cut off.
So, is the TCM able to read the range sensor correctly?
Does the scanner show P or N when it is P or N?
The range sensor consists of four switches.
Of those switches, T41 and T42 are both closed at N and P.
If there is no DTC in R or 1st, T41 may not be closed.
If there is a DTC in R or 1st, T42 may not be closed.

There are two P0841 listed, but is one of them a mistake in P0814?

 

[driconrikus]

In other words, if the range sensor detects P or N, the connection between the ECM and TCM will be cut off.
So, is the TCM able to read the range sensor correctly?
Does the scanner show P or N when it is P or N?
The range sensor consists of four switches.
Of those switches, T41 and T42 are both closed at N and P.
If there is no DTC in R or 1st, T41 may not be closed.
If there is a DTC in R or 1st, T42 may not be closed.

There are two P0841 listed, but is one of them a mistake in P0814?

Sadly our scanner cannot read transmission range, but it can read the transmission codes. I might need to get a better scanner to see this data.

Also, yes my mistake, the other one is actually P0869.

 

[ikuo78]

You can also check with a multimeter.
This is the upward facing connector among several connectors.

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