5R55E transmission code p0720 error

[Michael Sefsik]

This past week I started getting the flashing O/D light and shifting anomolys, hard shifts, and slipping . The code read P0720, output speed sensor ckt malfunction. I took a chance and replaced the speed sensor. This did not fix the problem. Here is where it gets weird. It happens when I first start it and head down the road. After it gets warm, and I shut it off (Say a run to the store). When I start it to go home, the problem goes away and the lights no longer flash. But If I park it for a while and it cools off, the problem returns. As I said, I replaced the speed sensor on the rear of the transmission already. Where do I go next? Trying not to drive it right now because Im sure that slipping and hard shifting cannot be good for the clutches in the thing. Any help would be greatly appreciated.

 

[domct203]

Have you checked the fluid level? Is it red or brown?

When was the last filter change?

 

[Michael Sefsik]

Fluid is red, changed 6 months ago. Had a new rear main seal (on the engine) put on then. It was over full by a quart though. Ive drained it down to normal now. Just so strange how it clears after its warmed up. Im gonna do a full flush and see if that helps. The code is electrical though. So I may have to buy a service manual. As I cant seem to find the specific thing for that code, P0720, Output shaft speed sensor ckt malfunction. Are there any other sensors on the outside that could be causing the problem? Thanks

 

[domct203]

The main electrical connector to the solenoid pack can become corroded and develop poor connections, might be worth your trouble to check.

I believe there is a bolt that retains the connector plug to the transmission.

 

[Michael Sefsik]

Update. Turned out to be the connector that pluged into the speed sensor on the rear of the transmission had corrosion. I cleaned the contacts, filled it with dielectric grease and all is weel. Thanks for the help!!

 

[donalds]

Yeeyeee

 

[domct203]

Glad this all worked out!