MKP

Hello, long time lurker here, I can usually find the info I need with a search, but having a hard time with this one. Last night the CEL came on while on the highway, I scanned it and got P0741- Torque Converter Clutch Circuit Performance. Is it safe to assume that this is the solenoid? I've checked the wiring harness and everything appears normal. This transmission did overheat back in November(stuck in snow) but I've done the drain and refill bit several times as well as a cooler. Would it be worth it to drain and refill once more? It's a 99 4.0L if that helps. Thanks

CCKen

You can read the resistance of the solenoids from your TCM connector.

Below is the TCM connector pinout.

Access the TCM by removing the trim panel and knee blocker from under the steering column. The TCM will be to the right of the column.

Disconnect the batery negative post connector.

Unplug the TCM connector.

Using a quality digital Ohmmeter, read from pin cavity 11 to 24 (ground), and, in turn, cavities 12 and 13 to 24.

Each solenoid should read between 11 and 15 Ohms. The resistance in the wiring from the TCM connector to the solenoids might be around 1-2 Ohms so your readings may be a hair higher than 11-15 Ohms.

MKP

Thanks, very helpful. I got about 12.6 ohms at each pinout. That eliminates the solenoids, correct? Does that point to a bad TCM?

CCKen

It could be the TCM but the TPS signals to the PCM also go to the TCM. If no, or corrupted signals, are received by the TCM it could affect transmission performance.

If you go to the pinout you'll see that pin cavity 17 is the TPS signal input.

You can try checking for the TPS voltage signal at 17. With the key to RUN, probe pin cav 17 w/24 ground, and have a helper run the throttle open then closed. See if you get a voltage signal from the TPS.

For some reason, other people have tried this and couldn't figure it out.

Let me know how you make out.

Edit: 12.6 Ohms are good readings.

MKP

Once again Thank You! I've got 0.90V at closed throttle and 4.12V at WOT.

CCKen

That works.

Hate to suggest changing the TCM without further troubleshooting.

P0741 doesn't show up in my '99 manual, nor in the 2000 diagnostics manual.

What scanner are you using. Is it a kind you program your vehicle in its database. If not, it may be tossing out generic codes that do not apply to a '99 xj.

MKP

Okay, thank you again. It was a scanner I borrowed from O'Reilly's, so I don't know much about it. But it didn't ask about specific vehicles. I'd go back but its a 25 mile drive, and I'm not sure what that may do to the Jeep. The nearest shop charges $30-$40 just to scan, guess I may just have to bite the bullet. In the forums I read about a P0740 code, does that sound more appropriate?

CCKen

P0740-SOLENOID C FUNCTIONAL FAULT

When the solenoid is energized and the Engine RPM does not equal the
Transmission’s Input Speed RPM or when the solenoid is deenergized and the Engine RPM equals Transmission input RPM.

Possible Causes:

TPS DTC P0122 PRESENT IN THE TCM
TPS DTC’S PRESENT IN THE PCM
TCM DTC’S P1748 AND/OR P1749 PRESENT
INTERMITTENT WIRING AND/OR CONNECTORS
TRANSMISSION OIL BURNT AND/OR CONTAINS EXCESSIVE DEBRIS
INTERNAL TRANSMISSION

Does your transmission go in to and out of overdrive okay?

Maybe when you overheated your trans the fluid got burnt. Maybe you should do the drain and refill thing to get the old fluid out as much as possible.

Of course, use Dexron III/Mercon ATF.
TEST ACTION APPLICABILITY
POSSIBLE

MKP

I've done that a few times, but the fluid still isn't clear red yet, more of a brownish red. After looking through the possible codes better, I'm pretty sure it's code P0743-Torque Converter Clutch Solenoid/ Trans Relay Circuits
An open or shorted condition detected in the torque convertor clutch (part throttle unlock) solenoid control circuit. Shift solenoid C electrical fault - Asin transmission-
OR -
An open or shorted condition detected in the torque convertor part throttle unlock solenoid control circuit (3 or 4-speed auto. trans. only).

2 descriptions on the site I saw. After scanning I'd forgotten the code number but could remember the problem described by the scanner. Guess I'll drain and fill one more time and see if that helps. Once again thanks for the help.