my 2nd gen FC (automatic) was runnig great, and still does however the engine light came on today and the RPM gauge stopped working.

I had rust proofing done 2 days ago, if that is of any help.

Any feedback will be much appreciated.

 

btt

 

Please specify year next time. It's an 89 (checked your profile), right?

The fact that you have done work underneath and have the troubles indicated makes me suspect they got to your speed sensor, mounted to the tranny at the end of the speedometer cable. Have a look underneath.