42RLE and P0740 code

[mt_]

I have an '06 Rubicon with a 42RLE and as I was driving around yesterday, the check engine light popped on and the code it threw was P0740 (and P0700). I've read some stories on the forum about this code and now I'm a bit worried for the transmission. What are some of the first things I should be checking? So far I have checked the fluid level (while hot and running) and it is at the correct level, and I looked at the electrical connections on the transmission and didn't notice anything obvious. I plan on checking them again, since I haven't checked them before I don't really know what I'm looking for other than a broken wire or maybe a short.

I put in the wranglerfix PCM in August '23, and shifting and idling still are smooth so it doesn't feel like there is a major internal problem, at least not yet. I know it may still feel normal and then get rapidly worse over time, so I want to address it now.

A little over a month I had a coolant leak that turned out to be a radiator cap, but I accidentally let the coolant get below the top of the radiator, there was residual coolant sitting on top that I saw and thought was the coolant level, so I drove home with some coolant missing. The engine temp didn't increase above normal operating temperature, but could the transmission coolant have gotten too hot?

I just had the rear main seal replaced at a shop within the last week, I don't think something could've happened during then to cause this, but I plan to talk to the guy who worked on it to get his opinion sometime soon.

 

[AndyG]

Torque converter slipping.


First check the wiring like crazy - fanatically. Feel wires for cracks or damage.

The harness is known to rub at the dipstick.


- remove both speed sensors and clean them

- drop the pan, do fluid and filter and check for metal- closely.

Clear the code and see what happens.

I wish there was a sure answer, but there isn’t. Even pro shops guess. A good tech can use a laptop to watch the TC lockup.


Low line pressure is the root cause ....mine turned out to be a failed torque converter at 58,000 miles.

How fast does the code come back once you clear it? If its every 20 miles or so your TC is not staying locked up. It takes 3 out of parameter t/c events within a certain time frame to trigger the code - mine was like every 23 miles- you could set your watch by it basically. Your speed and driving conditions will affect that- you need to be on the open road for consistent results. Bad fuel mileage will he evident also.

PM me if needed.