Can someone advise on how to reset the check engine light on my 91 240 wagon? I've had it to the mechanic but he forgot to hit the reset. Please note it is Standard Shift just in case this effects the reset location.

Thank You.

Do you mean the "service" light, or the "check engine" light?

The service light, which comes on at 5,000 mile intervals, can be reset by removing a small rubber plug from the instrument panel cover (near the speedometer), and pushing the button with a slender instrument, as noted in one of the other responses. Older models (pre '88?)required reaching up behind the instrument panel to push a button on the back of the speedometer.

If it's actually the check engine light, it can be reset quite easily by pulling out and re-inserting the number one fuse. This circuit runs the fuel injection pump and the ECU. Since there's no battery in the ECU (unlike your home computer), any fault codes are erased until the ECU detects them again.

My 1990 sedan has a reset light on the instrument panel, in the bottom right corner. I use a long allen wrench or small screwdriver and put it into the hole and push (~ 3lb force). you'll hear a click.

Don't know if this is the "right" way or not. I disconnect the battery for the count of ten.

I don't know how you are meant to do it either. I disconnect the battery for a while and then hook it back up. This means that my car runs very poorly until it figures out how to set the mixture again.