jakefinley007

Hello all i just bought my first 1999 jeep Cherokee it is 4X4 4.0L. And it has the CEL code p0740 torque converter circuit malfunction, The jeep was sitting for two years and the previous owner said when it was parked it did not have a CEL until it was started about 2 months prior to me buying it. Since buying it i replaced the TPS Because i had low idle around 730 RPM after replacing my idle went up to around 860-900 im sure once i put some injector cleaner in that will raise it a little to, Checked all 3 solenoids from the TCM connector and got about 13 ohms on all 3 also checked the brake light sensor visually and that seems to be fine. The jeep seems to shift fine too i got it up to around 50 and didn't feel any hesitation. I've also read that it could also be the transmission fluid being to dirty, Witch it defiantly is and i plan on doing a full flush. Any other suggestions? I live in NY so i cant pass inspection with any CEL on the code also comes on immediately after resting it to. Thank you for the help

tjwalker

First of all, congratulations on your 99 XJ! It is one of the best years for the XJ in my opinion, but I may be a little biased as I have one!

At the bottom of this reply is a link to the basics on the P0740 code.

You definitely need to start with getting clean transmission fluid as job #1. You may need to do up to 3 drain/fill/drive cycles to get to clean fluid. I wouldn't recommend any transmission fluid unit that actually "flushes" using pressure on an older transmission that hasn't been maintained well with fluid changes, as it can create problems. If it is a unit that just uses the transmission pump itself for a gentle 1-1 exchange, that is better, but I would still contend that it is safer to do a number of drain/fill/drive, repeat until fluid stays red.

Use Dex/Merc compatible fluid, NOT ATF+4, no matter what you may hear.

If getting fresh fluid doesn't loosen up your torque converter enough to start working properly, then consider some of the other options listed within the below link.

**BTW, 750 rpm give or take a few is a fine idle rpm for the 4.0 Doesn't need to be higher than that.

https://repairpal.com/obd-ii-code-p0740

jakefinley007

Thanks for the reply TJ, I was planning on dropping the trans pan and replacing the filter and draining the torque converter should i do that or just drain at the drain plug and top off the fluid?

tjwalker

The AW4 filter is simply a screen and usually does not require replacement. I would just drain and fill the transmission pan using the drain plug.......

jakefinley007

Ok thanks i just did my first drain today. The transmission fluid was very dirty i added some new drove it around the block a few times checked the fluid and its now red on the dipstick not brown, reset the code and it came right back. Should i drive it some more and do another fluid change?

tjwalker

If it is red, then drive it for a few days. Then try to clear the code again. The new fluid may not work instantly but may work over a little time and some miles.

New fluid has some "detergents" of chemical makeup which don't work instantly; they need a few miles to do their thing and clean the passages inside of the transmission and torque converter.

The above is not guaranteed to be a fix for you, but it really should be done first and regardless to extend the life of your transmission and before you move onto more complex possibilities that are detailed within that link.

Good luck and keep us updated!

dave1123

Yeah, I've been driving my 2000 WJ with a P0740 code for 6 years because after all the checks and diagnosis we've done, the problem is the torque converter clutch itself and I ain't ripping it apart just to gain 200 rpm less at 65 mph! On one long 250 mile trip last summer I got 26.4 mpg driving 70 mph with 90* outside air temp, no A/C, and all the windows down! Who could ask for more than that?

jakefinley007

X1997J

My WJ has the same code but mine won't shift into it's finally gear.

dave1123

New York. It won't pass inspection with any CEL on, but I can clear it, then drive it until the monitors clear, then hurry and get it inspected before the code comes back on. If I don't make it, I have to do it all over again! It usually takes about 250 to 275 miles before it comes back on, but if I keep checking the monitors, I can usually get it done before it reappears.

The torque converter clutch is not a gear. It's just a lock-up for the converter to eliminate it's slippage and reduce the heat buildup. It makes it like a manual trans with a clutch, a positive drive from the engine. It disengages when you hit the brake because if it didn't and you come to a stop, the engine would stall. You can tell when it's engaged. Lift your foot off the gas at 65 mph, the engine will change tone, but the rpms won't drop at all. It it's not engaged, there should be about 200 rpm drop when you lift your foot. Mine works some of the time, but if it doesn't long enough, the PCM will set the code.

jakefinley007

So today i cleared the code and took it on a longer drive and got it up to 60 MPH and my RPMs were around 2015. I drove for about 15 minutes on and off the express way and the code didnt come back until i reset the jeep witch make me feel like its the TCM or wiring problem. How else could the code trip so fast when before it even gets the chance to check it?

jakefinley007

JAFO-1020

Information for anyone looking to this thread to help diagnose p0740 code. This code is specifically "torque converter lock up circuit / open" This code specifically means an electrical problem (open circuit) was detected by the ECM or TCM. An open circuit is the presence of a break or failed connection in the circuit, so you need to look for broken wires, connectors not connected or not making good contact, or a bad solenoid (no continuity through the coil)

This code is not activated by low fluid levels, dark or burnt fluid, worn clutches, or slippage of any mechanical parts. So while it may be very beneficial to flush and change the fluid in your tranny, it will NOT fix this code.

Papote

I too getting the same code on my 2001 Jeep Cherokee. I checked all connectors and found one electrical connector on the back of the transmission disconnected but can't figure out where it's supposed to go. I've checked everywhere I could think of and nothing. Any ideas or suggestions?

Ismael

I'm also getting P0740 code in my 2001 Cherokee and also have that same connector in your picture dangling around, did you ever find where it goes connected? did you fix your problem? thanks!