Need help identifying codes.

[Ryan Outland]

Hi everyone! I’m needing some help on identifying codes that my truck is shooting. I plugged my scanner in and the codes are 3, 17, 65, 66, 78, 81 and P0720. The problem with the truck is that I can get up to about 40 and it will stop shifting. It doesn’t do this all the time though. Sometimes it will shift correctly, but it’s getting worse. Can anyone help me?

 

[DodgeTx]

P0720 is defined as a Output Speed Sensor Circuit Malfunction

I cannot help you with the others, but its possible you have a speed sensor that has gone bad or grounding out, not allowing the vehicle to shift correctly at times.

 

[jefechingon]

@DodgeTx any suggestions on how to determine where / if the speed sensor is grounding out. Just replaced the sensor for second time within 5 months...and the P0720 code popping up again.
Thanks

 

[tron67j]

The best thing you can do is run a check on all wires and see if maybe you have a short to ground or power. Both result from loose or broken wires, or when wire insulation is damaged. For the age of the vehicle, it is a decent bet you have such a problem. Easy places to start are main connections, take them off and clean contacts and ensure wires feel solid with good connectors. Work backwards to main circuits such as battery, starter, and all grounding points. I had a problem with my gen 3 a few years back, had a reading that a O2 sensor was bad. Replaced it and reset code, came back soon after. Bought another O2 sensor got ready to replace but first ran through the wires, and taking off the connecting wire and testing it found intermittent continuity.

Good luck