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P0743 Code, needing help.

rolln40s

NAXJA Forum User
Location
North Alabama
I bought this 2000 XJ a couple weeks ago and can't figure out what keeps throwing this code. I have replaced all the following; reman TCM, reman ECM and all 3 new solenoids, new fluid and filter. I have tested all the solenoids, they all tested between 12.8 and 13,1 ohms and the ground was 0.3ohms @ TCM connector. All the wires looked good, I've checked all the fuses, still no luck in clearing this code. I had the battery unhooked for a couple hours today and the code came back as soon as the starter hit. I'd appreciate any help, anyone would have to offer. I've searched all over the XJ forums and google.. Thanks in advance..
 
What is the symptom when driving?

I had a similar if not exact CEL on my 2k, can't remember.
My symptom was that the tranny would not shift into 4th gear maybe even a torque converter lock up issue. Again can't remember exactly that was years ago.
Turned out to be the tranny shift linkage needed adjustment i think after dropping my Tcase an inch.

But the CEL after clearing only appeared after driving a while in my case.
In your case the CEL happens when starting the engine which to me smacks of an electrical issue.
But i'd double check the tranny shifter linkage just to be sure, could be a worn bushing or something.

If the tranny fluid level is ok and all else fails, i'd double check all the connectors and wiring from the tranny to and from the PCM.
 
Popping up right away at starting seems bizarre, since it shouldn't be trying to power the lockup. Seems like you've replaced or inspected everything short of the t/c itself.
 
When driving at an even highway speed, do the rpms jump a few hundred when you tapthe brake with your left foot (causing it to unlock)?
 
Thanks for all the replies. The jeep doesn't have any symptom , besides the annoying CEL. It shifts good and seems to go into OD. I know there is a trans crossmember drop on it for the lift (installed by the previous owner), I will have to check the linkage to make sure its been adjusted. Sounds like I have gremlins in this Jeep.:roflmao:
 
Are you installing the specified Dexron-III/Mercon trans fluid ?

Having the code pop as soon as you start suggests a wire harness/wire plug issue.




P0743 JEEP Possible Causes
•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
•Low transmission fluid level
•Dirty transmission fluid

Diagnose P0743 JEEP code
Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded wire plug terminals.

P0743 JEEP Tech Notes
This is an electrical problem code. Could be a problem to the harness to the Torque Converter Clutch (TCC) solenoid, the TCC solenoid connector or the TCC solenoid it self.
 
Is there any way that connection between the TCM and ECM could be losing this data? I would think if the solenoids tested good at the TCM connector, then there wouldn't be a short from solenoid to the TCM connector. Would the fluid make it throw this code? I bought it like this, the guy that owned it, did the solenoid, fluid and filter change. So i don't know what fluid he used. I'm sure he did it right, he sounded pretty picky about the things that he did to the Jeep.
 
Is there any way that connection between the TCM and ECM could be losing this data? I would think if the solenoids tested good at the TCM connector, then there wouldn't be a short from solenoid to the TCM connector. Would the fluid make it throw this code? I bought it like this, the guy that owned it, did the solenoid, fluid and filter change. So i don't know what fluid he used. I'm sure he did it right, he sounded pretty picky about the things that he did to the Jeep.
I never trust the prior owner of anything I've bought pre-owned to have done anything correctly. Always verify.
 
If you had a bad connection between the ECM and the TCU, you'd get a different code (P0700 as I recall). You said you checked resistance at the TCU connector for each solenoid to ground. Just stabbing at things to test, but did you measure between each solenoid? You should get 2x the normal resistance, unless you had some sort of short between them. If that were the case though, I'd expect shifting issues.
 
If you had a bad connection between the ECM and the TCU, you'd get a different code (P0700 as I recall). You said you checked resistance at the TCU connector for each solenoid to ground. Just stabbing at things to test, but did you measure between each solenoid? You should get 2x the normal resistance, unless you had some sort of short between them. If that were the case though, I'd expect shifting issues.

I checked each solenoid to ground. Pin 11 to 24, 12 to 24 and 13 to 24. I didn't test between each solenoid. Yea, there is no shifting issues at all. I just don't like driving with the CEL on. I'll go out and test between each solenoid, now. I did check the fluid a min ago, its about in the middle between ok-max. I did check it with it up to temp and in neutral on level ground.
 
So, I guess I should drain the fluid and fill with the correct fluid?
Drain and fill won't get it all out. You can try flushing it, but since the PO did other things, you should check on those while your at it. Im dead serious. Those solenoids (and anything else he's done) might be cheap Chinese garbage off of Ebay. If so, it doesn't matter if they are new or not.
 
Drain and fill won't get it all out. You can try flushing it, but since the PO did other things, you should check on those while your at it. Im dead serious. Those solenoids (and anything else he's done) might be cheap Chinese garbage off of Ebay. If so, it doesn't matter if they are new or not.

Ok, that will have to wait til the weekend. Thanks for all the help.
 
I checked each solenoid to ground. Pin 11 to 24, 12 to 24 and 13 to 24. I didn't test between each solenoid. Yea, there is no shifting issues at all. I just don't like driving with the CEL on. I'll go out and test between each solenoid, now. I did check the fluid a min ago, its about in the middle between ok-max. I did check it with it up to temp and in neutral on level ground.

The solenoids tested between 26.1-26.3. I probed every way that they could have been probed.
 
I got another code,after I hooked the battery back up after I tested the solenoids. I get P0705 & P0743. I don't know if that's normal or not but I doesn't come back after I clear the codes.
 
oh ok, that makes sense. Could the transmission Input Speed Sensor cause something like this? I tried to get a resistance reading on it from the TCM connector but either I couldn't make a connection or its bad.
 
oh ok, that makes sense. Could the transmission Input Speed Sensor cause something like this? I tried to get a resistance reading on it from the TCM connector but either I couldn't make a connection or its bad.




Maybe. I thought about that too, but wasn't sure if that could cause the code to pop up right away. It's the same sensor as the rear speed sensor if you wanted to compare readings. The front sensor doesn't output a signal when the t/c lock up. It doesn't actually see the input shaft speed, but reads off on of the front planetaries.
 
Ok, I'm going to try again this weekend and see if I can get a reading off it or rear sensor. I'll probably just test them at the sensor instead of going through the TCM.
 
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