Transmission codes immediately after coolant flush

[tyler711]

Hey, all. I have a 2006 TJ 4.0 auto, 101k. Bought it ~2 years ago with 92k.

This jeep was a bit neglected when I bought it - needed all new bushings, shocks, control arms, track bars, plugs, tires. I've changed most fluids so I know what's in there. It's never thrown any codes or run poorly for the 10k miles I've put on it. All in all it didn't seem mistreated but definitely had maintenance items overlooked. No tow hitch, no undercarriage scars to suggest much serious offroading.

I finally did an initial coolant flush this weekend - did 3 or 4 fills and drains of distilled water, draining via the rad and the block drain each time. Initial test driving was fine (probably 20 miles total) but today as I got home from work I got a CEL and I read codes P0740 (torque converter clutch circuit open) and P0700 (TCM). I didn't notice any odd shifts or behavior for the last few miles home while the light was on.

Could I have gotten a connector wet while draining via the block drain that might cause this? If so, what can I look for, check, or reseat?

The timing seems too good to be a coincidence... though if my transmission suddenly failed after putting 12 hours of love into the cooling system, I'd be ready to believe that, too.

 

[hear]

I'd want to take a decent look at the ATF on the dipstick (fluid needs to be red, not pink), but electrical is your most likely culprit.

 

[tyler711]

I did glance at the fluid and it's up to level hot. Unfortunately color vision isn't my forte so until I can get a second opinion I can just say it's reddish.

 

[MountaineerTom]

The ‘06 autos have issues sometime with the PCM’s and transmission issues. I'll tag @Wranglerfix for you so he will see this thread. Mark is very knowledgeable about the PCM’s and may be able help you out some here.

I got a new PCM from him in 2019 (I think) due to having hard 1-2 shifts and some other codes. I haven’t had any issues with it since.

 

[Christian.mers]

My first check was fluid, that was my issue. How’s it smell?? You can always take a picture and show us too.

If you clear the code and it comes back it’s typically electrical (could be pcm like @MountaineerTom mentioned or the solenoid pack.)

I’d make sure to troubleshoot a lot because a new PCM or Solenoid pack are both expensive

 

[tyler711]

Thanks all.

Given the timing proximity to the water flush, I think I'll start by trying to inspect the solenoid pack connector and harness as best as I can. I looked at the FSM, and it also has some specific instructions for diagnosing the 0740 (mostly around clearing the code and then testing thru scenarios that should trigger it again).

I saw WranglerFix's comments in other threads suggesting that PCM issues often exhibit some odd shifts (1-2 when cold I think I saw) which I've never had.

The fluid didn't smell particularly bad when I checked it, but I'll certainly give that a better look. I need to check the manual for proper checking procedure, too - I checked it hot with engine off but I forget if the TJ has a particular procedure.

This jeep looks like it's had a very slow trans leak since I got it - never drips, but oily trans near the cross member; I'll look more closely at that too. One thing that does scare me on this car is the oil pan is clearly new-ish, with way too much RTV - I hope the old one just rusted out, and didn't get smashed on something.

 

[Christian.mers]

The fluid didn't smell particularly bad when I checked it, but I'll certainly give that a better look. I need to check the manual for proper checking procedure, too - I checked it hot with engine off but I forget if the TJ has a particular procedure.

This jeep looks like it's had a very slow trans leak since I got it - never drips, but oily trans near the cross member; I'll look more closely at that too. One thing that does scare me on this car is the oil pan is clearly new-ish, with way too much RTV - I hope the old one just rusted out, and didn't get smashed on something.

Engine hot and running in Neutral. You want it at the max crosshatching but anywhere within is acceptable.

I had an awful pan leak, I could never find it but grab a uv light and some oil dye from Harbor freight or Amazon or something. You can tell where that bolt was getting extra leakage. My pan was over torqued and the pan bolts were pushing inwards towards the case (probably why the have so much rtv) take it off and use some wood to sit the lip of the trans pan on and a ball peen. And knock them down level. Buy a reusable LubeLocker gasket, this one.

 

[inline6aficionado]

Dumb idea: When I flushed my radiator I got coolant everywhere... maybe you got an electrical connector wet somewhere?

My 2004 WRX reliably throws an O2 sensor code every time I wash it because the connector gets damp... dries out and CEL clears. Dumb, but it happens!

 

[Christian.mers]

Not a dumb idea, that was my one of my ideas as well because coolant can essentially “pool” on the driver side but I thought against it because it would be less likely for the coolant to somehow travel it’s was all the back

 

[mrblaine]

Engine hot and running in Neutral. You want it at the max crosshatching but anywhere within is acceptable.

I had an awful pan leak, I could never find it but grab a uv light and some oil dye from Harbor freight or Amazon or something. You can tell where that bolt was getting extra leakage. My pan was over torqued and the pan bolts were pushing inwards towards the case (probably why the have so much rtv) take it off and use some wood to sit the lip of the trans pan on and a ball peen. And knock them down level. Buy a reusable LubeLocker gasket, this one.

View attachment 650619

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Unless the silly person let the RTV set up before they installed the pan, it is pretty difficult to distort the flange with normal install procedures and RTV. Metal to metal doesn't distort the pan. Someone likely used a crap gasket and did the overtorque thing. I prefer Mopar 3Bond given a choice.

 

[Christian.mers]

Unless the silly person let the RTV set up before they installed the pan, it is pretty difficult to distort the flange with normal install procedures and RTV. Metal to metal doesn't distort the pan. Someone likely used a crap gasket and did the overtorque thing. I prefer Mopar 3Bond given a choice.

my thought was that the pan was overtorqued with a crappy gasket and it started leaking so they thought the solution was rtv but it didn’t fix the initial issue nor did it fix the leak

 

[tyler711]

Dumb idea: When I flushed my radiator I got coolant everywhere... maybe you got an electrical connector wet somewhere?

Not sure if you were replying to me or @Christian.mers , but that is exactly my hope. I'll update back here once I have some time to do some poking around with the harness and re-test after clearing the codes.

 

[hear]

The wiring for the transmission is literally nowhere near the radiator, so unless you had a 2 year old running the operation I can’t begin to imagine how flushing the rad would’ve got the required connectors wet.

On the other hand the ATF & coolant are both in the rad you flushed, which has me wondering if you don’t instead have a fluid contamination problem.

 

[mrblaine]

The wiring for the transmission is literally nowhere near the radiator, so unless you had a 2 year old running the operation I can’t begin to imagine how flushing the rad would’ve got the required connectors wet.

And even if they did get wet, that means it can't be driven in the rain.

On the other hand the ATF & coolant are both in the rad you flushed, which has me wondering if you don’t instead have a fluid contamination problem.

That would be very bizarre.

 

[hear]

That would be very bizarre.

So is the alternative.

 

[mrblaine]

So is the alternative.

I didn't mean it in a bad way. I know the heat exchanger is in the lower tank, I've just never contemplated that it would ever be an actual failure that mixed fluids. While I recognize it is possible, I'd just never go there unless I was seeing something odd with either or both fluids. I suspect due to the higher pressure of the transmission, he'd see trans fluid in the coolant first.

 

[hear]

Yeah, that’s why my first question was about the condition of the fluid, because I couldn’t come up with a reasonable explanation of how the connector got wet (or why he never had this happen in the rain).

Maybe the PCM connector got wet, but it ONLY affected the TCC? Or C103/C104 took on water but everything else is still fine? None of it lends itself to an obvious root cause.

And then once it dried I would expect it to return to good, I guess it’s only been 2 days since the issue was reported.

 

[tyler711]

And then once it dried I would expect it to return to good, I guess it’s only been 2 days since the issue was reported.

Yes, it's been a busy week and unfortunately the Jeep has been benched since the light came on; I'll have time this weekend to take a look.
Current plan is to inspect the connector and pins, and probably just clear the code and see if/when it comes back.

 

[tyler711]

Well, I cleared the code this morning and put around 50 highway miles on today with no CEL or odd behavior... I may call this a fluke until it comes back again.

 

[tyler711]

I haven't been back in here in awhile, but the 0740 is persistent and would come on every time I had the jeep on the highway. I haven't been driving it much while I came up with a plan. Today I'm planning to just do a basic fluid and filter change (no flush) since I have no idea what's in there - at least I can get eyes on the filter, magnet, and get a bit of fresh fluid in.

Just got the skid down and someone has definitely been in here before. My plan is to drop the plan, get it clean, scrape all the RTV off both sides, and check that the pan is square on a granite countertop. I have a new rubber gasket and filter to install.

I see the rust on the pan now, and will probably order another, but would like to go ahead if I can right now. Based on these pictures, any extra advice from anyone here?