42RLE shifting weird and throwing P1776 code

jmbstudios

jmbstudios

Guitar Slinger
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Picked up a 2004 TJ 4.0, auto transmission on Monday. I've driven it 100 miles since.

I was out for a drive, came to a stop at a light, tok off and it was like the Jeep was in 2nd or 3rd gear... and it did not shift up or down. Looked down and the check engine light was on.

Pulled over, turned it off, restarted and it was fine. Next stoplight same crazy thing as above. Shut if off,, restart,, all good... Did that a couple more times and seemed to right itself and shifted fine for the rest of the drive.

I remember I had an OBDLink MX. Plugged it in and I got the P1776 code.

Solenoid?
Does my Jeep have Coronavirus?

Pretty bummed that 100 miles after I bought it this starts happening.

The jeep has a meticulous service history and the previous owner took great care of it.

Any help is much appreciated.

Thank you
 
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To start off with, I would suggest that you check your tranny fluid level (you didn’t mention if you did that, or anything else you may have done to the Jeep since getting it). But p1776 may be a more generic code than actual.

Welcome back to the Jeep club! I hope you make a lot of money - because Jeep’s are very, very, demanding.
 
Thanks. Ya know as OCD as I was when I looked it over and even checked the engine oil, I didn't check the trans fluid...... Don't remember if I got distracted or what.....

I will do that.

And oh yeah, jeeps are cash eaters.
 
I checked it while it was running. About 30min to an hour prior to checking I got done with a 20 mile drive.

I did not shift thru any gears with the brake on.
 
jmbstudios said:
I checked it while it was running. About 30min to an hour prior to checking I got done with a 20 mile drive.

I did not shift thru any gears with the brake on.
Click to expand...

Depressing the brake doesn’t do anything, EXCEPT maybe keeping you from running over the dog or ripping thru the walls and door of your garage. 😂
 
Before I finished that drive where it was acting up I did put it in 1st at a stop light. Then shifted to 2nd then D when I accelerated.

I've read some info on issues like that indicates I should start looking at some electrical first.
 
jmbstudios said:
The jeep has a meticulous service history and the previous owner took great care of it.
Click to expand...
How many miles and what's the service history of the transmission (fluid and filter change intervals)?

P1776 means that the PCM detected that the L/R solenoid is stuck. The PCM then placed the transmission in limp mode (2nd gear) to reduce the likelihood of damage.

If the fluid is not low, since the Jeep is new to you, I would then suggest starting with a fluid and filter change. Fluid must be ATF+4. When you remove the filter make sure the o-ring comes out of the valve body. When you install the new filter, make sure the o-ring slides into valve body without getting pushed onto the filter neck. Expect to add in 5.5 quarts with a filter change. The service manual says 4 quarts, but 5.5 should get you right between the hot minimum and maximum marks on the dipstick.

The solenoids can get gummed up if the fluid is not changed regularly. While you have the pan off, either add a drain plug or get a pan with a drain plug, like Dorman. The service intervals for the 42RLE are 60,000 for regular service and 30,000 for severe service. Get used to changing the fluid frequently. If you plan to go off-road in the desert you'll also need an axillary cooler.

If the fluid level and condition are not the issue, you can move onto wiring or corroded connectors. It's probably best to reference the FSM and use a multimeter to check voltage continuity. Only after all of this would I replace the solenoid pack, which is not a simple procedure.

The steps for troubleshooting P1776 begin on page 148.

https://wranglertjforum.com/attachments/2004-tj-service-manual-pdf.14043/
MrMark52 said:
Yep - you need to read up on the PCM issues that ‘04-‘06’s have. Fortunately there is a reliable fix, although from the few threads I’ve read about it, I’m not sure that the problems your having are part of that failure.

We lucked out when we bought Oreo a couple of years ago - at least in that regard. 😖🤯
Click to expand...
2004 TJs are not affected by the PCM issue. They use a previous generation PCM and the TCM is mounted on the driver side fender.
 
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I looked at the transmission control relay and it had a small amount of gunk on the connectors. I cleaned them and plugged it back in. Then I took it on a 15 mile drive and never had the issue come back. Ran another scan and no codes popped up. It displayed everything was OK.

Currently- 160,500 miles.
According to the service records the transmission was serviced at 40k, then at 81k, then at 123k, last report was at 159k right before I bought it.
Right now it's at 160,500 miles.
 
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