Hey all, I recently changed the trans fluid on my 2001 (didn't drop pan and do the filter, just fluid). A couple days later, my CEL came on for P0740 which I've read is related to the solenoids. My truck has some pretty bad shift shock and the shift from first to second gear is sometimes harsh. That was why I changed the fluid in the first place but it seems like crazy timing for the light to come on right after changing the fluid. I've checked the dipstick level multiple times and it's within the safe range.

Is the best course of action to replace those 3 solenoids or to just do a complete fluid flush? Seems like the correct way to fix it is to do the solenoids, but some people have gotten rid of the light with the full flush. Also, will replacing those 3 solenoids most likely get rid of the shift shock?

Any input is appreciated. Thanks!

 

Test the solenoid circuits before you drop the pan or anything else. Did you use DexIII/Merc fluid?

Here's a thread on testing the solenoid circuits: https://www.cherokeeforum.com/f2/doe...-legit-195669/

 

100% correct. Test before spending

 

@IJM yes used DexIII/Merc. Roger that on checking circuits first, and thanks for the link to the other thread. So I guess it could be a handful of other things besides the solenoids, that just seems to be the most prominent issue from what I've read - is that fair to say? Thanks again

 

Yeah, that's probably a fair assessment. It's a process of elimination game, really, which is always fun in the middle of January.

 

Lol seriously. Also, the below is in post #13 of that other thread. When they say remove the connector from the TCM, if I do that, then how is it communicating with the actual solenoids when I test it? Or is there more than one connector and I'm just missing something?

Resistance Checks:

Disconnect battery negative post connector.

Use a quality digital Ohmmeter.

Remove the connector from the TCM.
________________________________

 

It's been over a decade, so my memory may be a bit fuzzy here, but I think the idea is to measure the resistance of the circuit between the TCM and solenoids, so you're using the multimeter probe on the connector (pins or sockets, can't remember which) to send a current through the circuit to the solenoid. IIRC, the other probe just goes to ground somewhere. You're not actually testing resistance through the TCM itself.

Sadly, CCKen passed a few years ago, because he was a huge help on stuff like this. Fortunately, he left a lot of very detailed posts on this forum.

 

Ah that makes sense (that I'm just bypassing the TCM and testing directly at the harness connector). The diagram in that other thread looks like the TCM itself though and not the harness connector. So will have to figure out which pins/sockets on the harness correspond to the solenoids somehow. Although I suppose I could just test through the TCM assuming it's good (leaving the harness plugged in and everything), no?

 

Unplug the tcm & shift manually. All gears working? It is an electrical issue.

 

So I just tried doing resistance tests on both the TCM itself and the wiring harness that plugs into the TCM (following the steps in that other thread). I could hardly get the voltmeter to read anything at all. I tried just moving the probes on the voltmeter around randomly to different pins on the TCM and occasionally I would get a reading but that was it. Any thoughts as to why this is happening (or not happening lol)?

 

Voltmeter or multimeter set to resistance mode? You're trying to measure resistance and not voltage.

 

Sorry shouldn't have used voltmeter. It's a multimeter. This is the one I have. Turned the dial down to the Ohms/omega symbol section and tried it with the dial turned to various numbers within that section

 

Set the dial to 200 on the bottom. You're looking for the resistance to be between 11-15 ohms. On a 2001, the TCU is under the drivers side and a little harder to get to. Below is the connector under the hood on the passengers side that's easier to get to. S3 is the solenoid that controls the torque converter.

 

Here's the connector at the 1992-2001 trans computer. Measure on the wiring harness between 11 and 24 for the t/c lockup solenoid.

 

Thanks for all this. Had the multimeter set to 200 but still wasn't reading on the TCU or the wiring harness that plugs into it. Maybe I'll try testing resistance at connector under the hood though - which socket on that connector is the ground?

Worst case I'll drop the pan and test the solenoids themselves. Want to get in there and change trans filter anyways.