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Pete, Automotive Mechanic
Category: Transmissions
Satisfied Customers: 29037
Experience:  GM and Mercedes vehicle technician.17 years experience.
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I have a 2002 jeep grand Cherokee with a 4.0l and automatic

Customer Question

Hello Chris
I have a 2002 jeep grand Cherokee with a 4.0l and automatic trans. The problem is the transmission goes into limp mode with p0720 code. I have replaced the neutral safety switch, speed output sensor, pressure solenoid, pressure transducer and pcm. any other suggestions
Submitted: 1 year ago.
Category: Transmissions
Expert:  Clayso replied 1 year ago.

Hi James, I'm Clay a certified master automobile technician with 30 years of automotive repair and diagnostic experience.

P0720 most commonly sets for the Output Speed Sensor (OSS) circuit. I'm not sure if you checked this circuit or simply threw a part at it. There are a couple different ways and a couple different places to check this circuit. Check the resistance of the OSS it should be(###) ###-####ohms. You can also verify the resistance at the PCM C2 connector on pins 25 and 28. Check also for an AC signal from the OSS with a voltmeter on the AC setting and the output shaft spinning, this will verify OSS operation and a loose or out-of-position reluctor on the transmission output shaft.

I hope this information is helpful. If you have any questions or run into any problems let me know.

Kindly rate my assistance in a positive manner so I may have credit for helping you.
Positive ratings are greatly appreciated.

Expert:  Clayso replied 1 year ago.

Hi James. I noticed you had viewed my answer, and I hope the information I gave was helpful. Let me know if you have followed through with my recommendations. If you have any questions, please let me know.

Positive ratings are greatly appreciated.
Thanks so much.

Customer: replied 1 year ago.
Sorry, was out of town....I checked everything you requested and everything thing so far checks out. still not working.
Expert:  Clayso replied 1 year ago.

Hi James, thanks for getting back to me. No problem, I had a pretty busy weekend myself. Using the diagram in the link below. Check the circuit from the PCM to the OSS sensor by disconnecting the negative battery terminal. Then disconnect the White C2 connector at the PCM, check the resistance between the terminals 25 and 28 and let me know how much resistance is on this circuit.

PCM Connector C2

If everything checks out electronically you may have internal transmission problem(s). With the transmission control relay removed will the transmission shift manually through all gears?

Let me know

Customer: replied 1 year ago.
I have 750 ohms on that circuit. I don't think I have transmission relay. I can reset the computer and the trans works fine, but as soon as it shifts the engine light comes on and when I restart it will not shift until I reset computer.
Expert:  Clayso replied 1 year ago.

I'm going to opt-out and repost this question. Another expert may have more experience with this problem.

Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Have you inspected the wiring fully leading from the transmission to the computer for any pinched,shorted or damaged wiring at all needing repaired or repalced?

Let me know so we can continue,thanks Pete.