Friend's 2000 Grand Caravan. Check engine light came on and stays on. She took it to a quickie service place; they told her code indicates some sort of emissions problem, but they checked the emissions while renewing inspection sticker and said nothing wrong. They also topped up low auto tranny fluid.

Since then, check engine light still always on, but now she said it acts like tranny is slipping: step on gas, nothing happens for a few seconds, then car engages with a jerk and off she goes. Says this is getting worse, and also she smells something burning.

Is this two separate problems or one? Is it necessarily a bad tranny or could something like an O2 sensor cause this? Could topping up with wrong tranny fluid make tranny slip?

I do a lot of my own car work but never on auto trannys and have never worked on a Grand Caravan (or any Dodge or minivan for that matter).

 

Check the fluid level and check for leaks, also may be bad pump or leaking seals internally cvausing delayed engagement.