42RLE automatic transmission temp fluctuation

[DrewG71]

I have a 2006 auto transmission the temperature fluctuates between -19 and 170 at rest within the space of a few minutes, Trans works fine other than that.
Any ideas. Apart from replace the range sensor.

 

[Christian.mers]

Do you have a gauge or are you using your OBD II?

 

[hear]

Sounds like a bad ground. 170F sounds like more or less the right operating temp, -19 is probably what the gauge is calibrated to read when no voltage is present.

But wait, do you have an aftermarket gauge, I assume? Unless you're reading it via OBDII...

 

[Christian.mers]

My thought too, you can’t replace the tft sensor by itself, you’d have to replace the entire solenoid pack but if you’re shifting perfectly fine then I don’t see something so vital to be the issue?

 

[DrewG71]

Thanks for replying. The readings are from one of those professional zuess scanning tools the auto electrician used. While driving the temp reads fine. When stopped the temp jumps from extreme high 170 degrees celcius to -19 celcius.

 

[Christian.mers]

with a good scanner you know you’re getting precise and accurate readings. You’re not having any shifting error so it lets me know your solenoid pack (temp sensor and major valve body component) isn’t bad.

Here’s a troubleshooting list:
1. Take for the 8 pin connector on driver side of trans and unplug/inspect.
2. Inspect harness by the exhaust and bellhousing, could definitely be intermittent due to a melt or frayed wite
3. Check grounds, not just trans area

Are you having any other issues that could help pinpoint the issue??

 

[DrewG71]

with a good scanner you know you’re getting precise and accurate readings. You’re not having any shifting error so it lets me know your solenoid pack (temp sensor and major valve body component) isn’t bad.

Here’s a troubleshooting list:
1. Take for the 8 pin connector on driver side of trans and unplug/inspect.
2. Inspect harness by the exhaust and bellhousing, could definitely be intermittent due to a melt or frayed wite
3. Check grounds, not just trans area

Are you having any other issues that could help pinpoint the issue??

Yes i had an auto electrician clean the pins and plugs, check the wiring. He did a test drive and got good temp readings while operating the vehicle. But the moment he stopped the jeep he was getting the temp jumping from -19 to 170 degrees celcius ( i assume it was celcius ) the whole trans was rebuilt about three years ago for $5000 Australian.

 

[DrewG71]

Sounds like a bad ground. 170F sounds like more or less the right operating temp, -19 is probably what the gauge is calibrated to read when no voltage is present.

But wait, do you have an aftermarket gauge, I assume? Unless you're reading it via OBDII...

No after market gauge. Readings are coming from zuess Electronic scanner

 

[Christian.mers]

That $5000AUD I’d expect a new solenoid pack but there’s always a possibility of it not being replaced. Have you noticed anything off with converter lockup or overdrive?

 

[hear]

The smoking gun here is the -19. For some reason the sender stops sending or the PCM stops receiving the signal, and interprets no voltage as the min temp it can report.

 

[DrewG71]

That $5000AUD I’d expect a new solenoid pack but there’s always a possibility of it not being replaced. Have you noticed anything off with converter lockup or overdrive?

The only issue it has is sometimes there's is a brief shudder between 3rd to fourth gear id say, particularly under quick acceleration.

 

[DrewG71]

The smoking gun here is the -19. For some reason the sender stops sending or the PCM stops receiving the signal, and interprets no voltage as the min temp it can report.

Yes that is interesting thanks for the observation.