I've had my 05 srt for almost 2 weeks and this is the second time this code (p0720) has come up. When it happens the trans will not up shift and of course the abs and bas lights come on. Any typical area to look at or do I need to start doing some electrical diagnosis?

 

Output speed sensor malfunction. My first guess would be, transmission circuit board not responding. But it also could be something as simple as wheel speed sensors or rings. Are you disconnecting the battery to reset the system , so your able to drive again?

 

It did shift on it's own after a second or two, so no I didn't have to disconnect the battery. Why would a wheel speed sensor cause that? I can see it causing an abs light but not the shifting problem.

 

The code is, Output Speed Sensor Malfuction. They work to report wheel speed , wheel slippage. It is only one of my hypothesis. Have you checked your fluid levels? Start with the basics. Like I said , my bet is the transmission conductor plate.

 

What he said ^^^^^^^^^^

 

There is a speed sensor on the transmission as I recall, I'll check it out.

 

What is the transmission conductor plate? Mine is doing the same thing. I picked the car up as a school project and it has been sitting for 4 years. Speedometer is not working so I thought they might be related.

 

It is what is like the valve body in the 722.6 transmission, it connects 5 shift solenoids and a speed sensor and maybe some other components to the transmission control module.
There are tons of howto videos on uTube about changing it.

 

Ok I will look them up. Thanks for your reply I appreciate it. My students are excited to get to get started on it.