P0740
 

I just started day 2 of my trip not far from home at all and this code came on. Jeep seems to be running great.

I'll make sure my trans fluid is ok but anyone know of anything else?

I have not dealt with this, nor can I recall seeing this come up on the forum much at all, and it seems when searching past links, many of them end with little or no input. I did a little searching since you're on the road and searching around is probably less conducive for you. This site seemed pretty informational -

https://www.700r4transmissionhq.com/...jeep-wrangler/

Besides checking the ATF level, are you able to monitor your ATF temp? If no obvious symptoms, seems like monitoring fuel economy might be a good place to start as well which would help pinpoint this as a torque converter issue. At that point, seems it could be a wiring issue, torque converter clutch solenoid, or the TC, or gawd forbid the tranny itself.

You did an ATF and filter change recently correct? Hopefully this is just a fluid level issue.

Thanks buddy for the help As always. My jk feels like it's running perfect but code came back again. I added half a quart of Tranny fluid but I'm kinda spooked and may be turning around at this point. I have all summer to make this drive. Would rather not have tranny problems.

Here is what I found in regards to likely causes of a P0740. Seeing as though, you just finished wrapping up changing fluid and fixing your lines, I would lean towards low fluid.

P0740 Jeep Possible Causes

• Low transmission fluid level
• Dirty transmission fluid
• Faulty torque converter clutch solenoid valve
• Torque converter clutch solenoid valve harness is open or shorted
• Torque converter clutch solenoid valve circuit poor electrical connection

Here are the levels from the service manual. You likely don't have an OBD2 reader to get actual trans temp, but based upon my recent monitoring of my trans temp, under normal driving conditions after warmed up, I found that when when engine temp was at 205deg F (ie 12 O'clock on dial), that my trans temp was at 145-150deg F. So I would use that as a baseline to check your trans fluid level to see if you need to add.

https://drive.google.com/uc?id=178nE...CB8ow1Ks8oJYkH

FYI, my actual trans temp readings where I show engine temp in relation to auto trans temp. Since you do have a engine temp gauge, this may help put you in the ball park of actual trans temp to be able to figure out if you're low on trans fluid or not.

https://drive.google.com/uc?id=11dU3...oPWJV45BXUpK0G

https://drive.google.com/uc?id=11kT0...OqvubgRN6gkiBK

I put half a quart in just Incase on my way back. I have a house down here so I'm only one hour away. Heading back to my house and I will see if the check engine light comes back with 1/2 quart tranny fluid in. If it does I'll add the full and if it still comes back it's going to dealer under the lifetime power train.

Just sucks after spending all that time trying to make it run perfectly.

I feel that. I spent a ton of time last year making sure all was good prior to my trip to the sand dunes. Arrived in the Dunes and an hour later my "Hot Oil" light came on which I didn't realize at the time is actually the light that comes on when your trans fluid is hot. I got a trans cooler sitting in my garage waiting to be installed.

If you own a JK without a transcooler it's done for. Learned that with under 50k on mine and got the mopar. Light never came back.

What worries me most about continuing on is that if it were low fluid it would have thrown this code a month ago when I did the service? That seems more logical.

I've been driving it for at least 3k since the Trans service and no issues. All of a sudden today it's 2 in a row.

Definitely could be electrical but that's almost just as bad or equal on a road trip to mechanical. Stuck is stuck.

My thought was that the additional load of your trip may have caused it. That's just based on my hot oil light experience. I never seen the hot oil light until I started playing on the sand hills after owning my JK for 9 years.

I'd agree in being skeptical continuing with the trip with this particular code being thrown. Not like something that is truly superficial like an evap code. That sux. You're always good at following up. I'll be interested to see where this ends up as it's not a code I've seen talked about often.