My sons 1987 300TD with 190K miles recently was sluggish and stalling out on him. Tonight I replaced the pre and main fuel filters and tested it out. Seems to be pulling hard through the gears just fine now.

The question is I noticed his check engine light is ON when the headlights are ON. If I shut the headlights OFF the light goes out. I've never seen anything like this before? His Hazard light switch has gone bad and I thought it may be related to that. I was able to hold his hazard switch just right and this makes the hazards come on but when I did this the engine light still behaves the same.

Any idea why the engine light comes and goes with the headlight switch? Got me puzzled and I'm fairly good with cars. Mind you this is our first diesel but this does not necessarily sound like a diesel issue?

Can the car be scanned for a code? I have an OBDII type scanner but I think this vehicle pre-dates standard scanner connectors. How can I clear this and or check the code? I can make a jumper wire harness to test a code if needed. Just need some suggestions. Sorry for the many questions.

 

Well I need to examine his car a bit closer. I think we may have gotten the bad bulb indicator confused for a check engine light. Dooohhhh!