Long story short... O2 sensor wire melted after being caught in driveshaft and then pushed into exhaust pipe... replaced wire and O2 sensor. Kept getting O2 sensor fault code turned out to be a bad fuse box... just replaced fuse box... cleared codes and took it for a drive... now the M & S symbols are flashing when I put it in gear and the transmission while it shifts into reverse and drive only goes into 2nd gear and will not shift up or down while driving. I haven't checked the codes yet but am I correct in assuming it is most likely going to be the TCU?

 

Maybe. What is your voltage? The trans ECU’s are very picky about voltage.

 

The battery was fully charged when this happened as it had been on the charger overnight.

 

Harv.... where would be the right place to check for transmission ECU voltages? Right at the module, or at connections to the transmission? My own 2003 has the M & S symbol flashing intermittently, and only in the winter when temps are cold. Glad for your advice!

 

Personally I would start by just checking the vehicle voltage anywhere, the Ultragauge would be a great place. If battery/alternator voltage is much below 12.5 the transmission ECU will complain

 

There are 14 different faults that can trigger the M&S lights to illuminate together. You can't know the cause without getting the codes read.

That said, and as others have written here, the most common cause of the flashing M&S lights is a voltage anomaly. Clean and check and double-check the battery terminals to ensure they are clean and secure.

If that doesn't address the problem, get the transmission codes read, or at least review the RAVE workshop manual to look for symptoms that match what you are observing.