Weird lockup issue?

Hello,

I have been having a strange issue with my 2001 Jeep Cherokee for the last few weeks and have had no luck getting it fixed. Randomly my Jeep has been stalling. The only code I am getting is p0743 (Torque Converter Clutch Solenoid). I have no CEL. I will be driving smoothly at any speed (stopped, 35mph in town, 55mph on the highway). RPM’s will start fluctuating wildly and cause the Jeep to buck and. Most of the time this leads to the Jeep stalling. You can put it in park and it will restart, although sometimes you have to crank it over for 5-10 seconds. It is fairly intermittent, one day it will happen 10 times in a row, the next you can drive with no issues.

-I replaced the TPS with a genuine Mopar part that didn’t help.
-I also replaced all the solenoids in the transmission which didn’t help either.
-Transmission fluid is new as well as the filter. Replaced when I did the solenoids.
-Inspected and tested the brake switch while driving. The converter unlocked when you tap the brake.


One point I wanted to add was today I was driving at 55mph when it started happening. The RPMs were jumping between ~1800-2500. Then the RPM did what looked like a full sweep. From basically 0 to over 6000 where it hit the needle then swept back. The motor was not spinning to 6000. Can the sensor that reads RPM cause the issues I’ve been having?

Any ideas other ideas what might be going on?

I am about to take it to the mechanic so any help would save me some $$$ haha.

I would suppose that the P0743 is a byproduct of whatever issue is causing the observed symptoms and stalling, and is not the root cause of the symptoms. The symptoms suggest a short circuit in the 5 volt CCD Bus circuit. This however does not mean you shouldn't bother to inspect the transmission wire harness and wire plugs.

I would start by confirming both the Crankshaft Position Sensor and the Camshaft Pickup Sensor are genuine Jeep parts. Next, visually inspect and test the wire harness to both sensors, looking for poor ground connections, wire plug corrosion, missing, bent, or pushed back wire plug pins, melted/chafed/cut wire insulation or otherwise damaged wires, and failed wire splices.

Confirm that the Cam Position Sensor synchronization is correct with an oscilloscope or a service shop DRB-III Diagnostic Tool.

Tim_MN said:

I would suppose that the P0743 is a byproduct of whatever issue is causing the observed symptoms and stalling, and is not the root cause of the symptoms. The symptoms suggest a short circuit in the 5 volt CCD Bus circuit. This however does not mean you shouldn't bother to inspect the transmission wire harness and wire plugs.

I would start by confirming both the Crankshaft Position Sensor and the Camshaft Pickup Sensor are genuine Jeep parts. Next, visually inspect and test the wire harness to both sensors, looking for wire plug corrosion, missing, bent, or pushed back wire plug pins, melted/chafed/cut wire insulation or otherwise damaged wires, and failed wire splices.

Confirm that the Cam Position Sensor synchronization is correct with an oscilloscope or a service shop DRB-III Diagnostic Tool.

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Just to follow up I broke down and took it to the mechanic. You were right it was a Crank sensor. Not sure why when I pulled the codes the first time it wasn’t there, but they pulled them again.

Just wanted to update the thread in case someone search’s with a similar issue.

YoTony said:

Not sure why when I pulled the codes the first time it wasn’t there, but they pulled them again.

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Glad you got it fixed. It's actually not unusual to not have a code for the crank sensor. You'd think the computer would be smarter about it, since it knows the engine it turned by watching the cam shaft sensor.

lawsoncl said:

Glad you got it fixed. It's actually not unusual to not have a code for the crank sensor. You'd think the computer would be smarter about it, since it knows the engine it turned by watching the cam shaft sensor.

Click to expand...

I agree.

When mine went I believe it was experiencing thermal failure. Pretty much would cause the Jeep to stall when she reached operating temperature.
She would start back up. Maybe stall again. Maybe I would get to where I was going.

No codes, weird gauge crap that I have read about, no sputtering, nothing the OP is saying his was doing. Just stall like you turned off the key.

As time went on it got worse and worse. The CPS resistance test came back as being good but I replaced it anyway.

Luckily it was the problem.

A lot of times those weird gauge issues can be caused by bad grounds which can also cause weird sensor issues. Even if the issue is fixed right now it may be a good idea to go though all of your grounds can clean/refresh them.

Crank Position Sensors can have intermittent “thermal failure”. The CPS/CKP fails when the engine gets hot, but works again when it cools back down.

Typical CPS Faulty Symptoms, (not all symptoms may be present, or occur at the same time) -

- Random stalling
- Starter cranks and cranks but engine won't start up
- Fuel gauge and voltage gauges may not work or display properly.
- You sometimes will have NoBus displayed on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.