42RLE issues

creepycrawly · Jun 26, 2016

Ive got a 42RLE that is giving me fits. Stuck in limp mode. I thought it was PCM so I replaced it and have the exact same issue. Its throwing codes:

P0731 first gear incorrect ratio
P0846 Trans fluid pressure sensor/switch B circuit range/performance
P0613 TCM processor
P1604 Manufacturer control Aux inputs/outputs

Anybody have any suggestions or know where I can find a cheap 42RLE in good shape? I know Daveys has them for about $600 shipped but I am trying to go a little cheaper.

kushKrawlin · Jun 27, 2016

Line pressure? ;D

RebelRider · Jun 27, 2016

When was the last service?

creepycrawly · Jun 27, 2016

kushKrawlin said:
Line pressure? ;D

I got some hose pressure for you!

creepycrawly · Jun 27, 2016

RebelRider said:
When was the last service?

Not sure. It's used, but from the look of the bolts on the trans pan, I would say a while ago.

RebelRider · Jun 27, 2016

A buddy had the same issues with his in his LJ.
He brought it to a Trans shop, and of course they said it was toast. He brought it back home and did a basic filter/fluid change and it hasn't shot any codes on almost 3 yrs now.

creepycrawly · Jun 27, 2016

RebelRider said:
A buddy had the same issues with his in his LJ.
He brought it to a Trans shop, and of course they said it was toast. He brought it back home and did a basic filter/fluid change and it hasn't shot any codes on almost 3 yrs now.

Awesome. I am definitely willing to try it. My concern is the tcm codes it's throwing. The previous owner had some welding done and they didn't disconnect the battery which is why I jumped straight to PCM. I am afraid I'll spend more on chasing the issue than a new (used) trans will cost.

RebelRider · Jun 27, 2016

I have the same Trans in my LJ. I weld to it all of the time with the battery connected.

creepycrawly · Jun 27, 2016

RebelRider said:
I have the same Trans in my LJ. I weld to it all of the time with the battery connected.

Trans pan will come off today.

RebelRider · Jun 27, 2016

creepycrawly said:
Trans pan will come off today.

Hopefully it fixes the issue. It's definitely worth a try. Just be careful re-sealing the pan. They can be a pain to seal off. I never use a gasket, just high temp rtv. Also be careful with the pan bolts. They strip very easily .

grcthird · Jun 27, 2016

If you had the P0613 code in both modules, I bet you have a wiring issue, something shorted out and causing the TCM to fail. The repair manual lists the TCM or wiring as the only 2 possible things that can cause that code to come up. The p0731 is setting due to it being in 3rd gear limp mode, and the p0846 probably is too because in limp mode it should max out the line pressure to keep the trans from having accelerated wear. Check all the electrical connections on the trans before you pull the pan, might save you some aggravation.

creepycrawly · Jun 27, 2016

grcthird said:
If you had the P0613 code in both modules, I bet you have a wiring issue, something shorted out and causing the TCM to fail. The repair manual lists the TCM or wiring as the only 2 possible things that can cause that code to come up. The p0731 is setting due to it being in 3rd gear limp mode, and the p0846 probably is too because in limp mode it should max out the line pressure to keep the trans from having accelerated wear. Check all the electrical connections on the trans before you pull the pan, might save you some aggravation.

Awesome info. Thank you. So, in your opinion, is the short frying the tcm? Aka do I have 2 bad ones now? They both exhibit the same symptoms.

grcthird · Jun 27, 2016

creepycrawly said:
Awesome info. Thank you. So, in your opinion, is the short frying the tcm? Aka do I have 2 bad ones now? They both exhibit the same symptoms.

I have seen short circuits fry computers, it's possible they are both toast. I have fixed transmissions that just had bad/dirty/wet connections before that threw all kinds of crazy codes. Definitely make sure the connections are good, if you have the time, ohm each circuit on the trans harness out to rule out opens, shorts to power, and shorts to ground. It sucks and takes a while to do but is the only way to eliminate if the problem is in the harness or trans side. I ran the codes through Identifix and nothing came up, usually common stuff that breaks shows up there.

creepycrawly · Jun 27, 2016

grcthird said:
I have seen short circuits fry computers, it's possible they are both toast. I have fixed transmissions that just had bad/dirty/wet connections before that threw all kinds of crazy codes. Definitely make sure the connections are good, if you have the time, ohm each circuit on the trans harness out to rule out opens, shorts to power, and shorts to ground. It sucks and takes a while to do but is the only way to eliminate if the problem is in the harness or trans side. I ran the codes through Identifix and nothing came up, usually common stuff that breaks shows up there.

Thanks for the help. I appreciate it. I'll let y'all know what I come up with.

creepycrawly · Jun 27, 2016

grcthird said:
If you had the P0613 code in both modules, I bet you have a wiring issue, something shorted out and causing the TCM to fail. The repair manual lists the TCM or wiring as the only 2 possible things that can cause that code to come up. The p0731 is setting due to it being in 3rd gear limp mode, and the p0846 probably is too because in limp mode it should max out the line pressure to keep the trans from having accelerated wear. Check all the electrical connections on the trans before you pull the pan, might save you some aggravation.

After talking with Daveys jeep parts, he said that the 2005 and 2006's are known for having broken wires between the trans and PCM at the firewall. Looks like I am gonna drop trans and start chasing wires. I have pretty much decided not to throw more money at it. If I can find any broken wires, Ill yank the motor and trans and go to an LS and 4l60.

RebelRider · Jun 27, 2016

creepycrawly said:
If I can find any broken wires, Ill yank the motor and trans and go to an LS and 4l60.

Now your talkin......

grcthird · Jun 27, 2016

creepycrawly said:
After talking with Daveys jeep parts, he said that the 2005 and 2006's are known for having broken wires between the trans and PCM at the firewall.

Got a body lift on it?

creepycrawly · Jun 27, 2016

grcthird said:
Got a body lift on it?

No sir.

creepycrawly · Jun 28, 2016

grcthird said:
If you had the P0613 code in both modules, I bet you have a wiring issue, something shorted out and causing the TCM to fail. The repair manual lists the TCM or wiring as the only 2 possible things that can cause that code to come up. The p0731 is setting due to it being in 3rd gear limp mode, and the p0846 probably is too because in limp mode it should max out the line pressure to keep the trans from having accelerated wear. Check all the electrical connections on the trans before you pull the pan, might save you some aggravation.

And the saga continues. This thing definitely has some wiring issues. The Fuse box under the hood has a ground wire ran from the ASD relay to the negative post on the battery. If you remove it, the jeep won't start. With it in place, the jeep starts, but the safety switch is bypassed and the jeep will start in any gear. I feel like I need to sort this out before I start looking at the trans. Any suggestions? The PO doesn't know what his mechanic did or did not do, so no help there.

Update: when I pulled the ASD relay out, I couldn't see what terminal the jumper was grounded to and now it won't start at all. I ****ing hate electrical work. I really hate someone else's :JRich:

electrical work.

creepycrawly · Jun 28, 2016

I am 99% sure it is a bad ground or short in the system now. I messed around and got it to crank. It will only crank in neutral now and not every time. I think I am going to look for a wiring harness because that will be cheaper than paying someone to troubleshoot it. Certainly not willing to throw a trans at it just yet. Anyone think it could be trans solenoid?

Got new codes this time. Got p0888 tcm power relay sense circuit.