I just put a Performance Accessories 3 inch lift on my truck, along with a big steel bumper, and of course, the truck decided to stop working today. I was driving at 60 when the torque converter unlocked, followed by erratic shifting. The truck later gave me a P0720 code, which says output shaft speed circuit malfunction. I quickly threw a new output shaft speed sensor in the trans and cleared the code, which helped for about 20 minutes. After that, the problem returned. Being that the lift I put on was a body lift, I suspect that I've got a bad ground or messed up wire on this circuit. So I was wondering if anyone had any ideas as to why this could be happening. I've worked on the 46RE before and I'm completely stumped. This is the second trans I've put in this truck and I really don't feel as if it needs a rebuild already. If any of the dodge guys have a flow chart on diagnosing a output shaft circuit malfunction I would greatly appreciate it if you sent that my way.

 

That sensor gets a five volt signal from the PCM, and sends back a modified voltage. That appears to be the only wires in the circuit. Might be just a poor connection up at the PCM.... check and clean them, see if it helps.

 

Already cleaned connections at pcm. I see a little bit of exposed copper behind the connector so I'll be ordering a new connector today. When I did my 46re swap I may have routed wires in a way that they could get snagged when lifting. My bets on a messed up ground or the connector. I also noticed a small amount of metal on the magnet of the old sensor. The amount didn't worry me but I'm starting to wonder if there is more to the metal chips than I initially thought. Might drop the pan down today to see if the pan has metal or clutch material at the bottom. The fluid however looks perfect and smells brand new. I'm also wondering if the solenoids can upset the sensor. I don't think this trans has ever had the solenoids serviced.

 

The output speed sensor works on exactly the same principle as a wheel speed sensor. There is a tone ring the sensor reads, and the sensor outputs a signal at a varying frequency, directly proportional to shaft speed. Given the nature of your symptoms, I would highly suspect a wiring issue, rather than an internal trans issue. however, it sure wouldn't hurt to check.

Do you have a scanner that will show that sensor value?

 

I have a really good multimeter and a couple of oscilloscopes in the garage. I'm gonna trace the connection as far as I can today. Also gonna look more into the exposed wire by the sensor. Greatly appreciate the feedback.

 

After inspecting the connector on the output shaft speed sensor I found that the two wires leading into the connector had loosened from the connector and crossed each other. This was what was causing my problem.

 

Cool. Gotta love the easy ones.