This is info from a 1988 240 wiring diagram manual.

Backup lights are switched on by the neutral/park starting inhibitor switch in the tranny shifter well.

There are two wires that go into the well for the b/u lights, a BL-Y from fuse #12, and a SB (black) that goes out to the rear lights. The BL-Y and SB wires go through a connector, so you can make a jumper to see if it's the fuse or the n/p switch.

First check the rear lights. That's the place that is most likely to give trouble. Pull the spare tire and remove the cover over the left side rear light.

Then set up the car so the back-up lights should be on, but the engine not running. Find the big connector on the left rear light where the harness connects to the circuit board of that light. Wiggle it up and down a bit and watch the lights.

The connection inside that connector to the circuit board get oxidized over time, and that may be the reason for no lights. Assuming, of course, that no lights is the reason for your post.

If wiggling the connector make the lights come on, there is a fix for that. Post back.

Good Luck,

Bob

:>)