Trip meter resets itself
 

So I buy this cool 2002 S40, love it... But, dude I got it from said "everything works..." (Long pause)... "Except, the gas guage" I'm thinking, that's cool, easy fix...good vehicle, good reputable manufacture. I'm happy. Filled it up with fuel, started my commuting routine. I commute 74 miles a day round trip. Since the fuel gauge will have to wait I was going to use the trip meter to measure my "bingo" limit on fuel. Started out okay, drove to work, 37 miles, so it's accurate. After work, I drive home. I hadn't noticed the trip meter until I got home, it was still at 37!! So the next time I started her up, the trip meter was at zero and the clock read 1200! I had just set it. So I'm asking, wassup with that?? To top that all off, I replaced the fuel pump and fuel sending unit. Now I have intermittent fuel readings, but mostly it registers empty. The wife and I ran out of fuel at a very inopportune time, and placed us on the shoulder of very busy interstate just outside of the fog line. Extremely unnerving for me, and terrifying for the old lady. So I really need to get this issue fixed. I appreciate any information on this, even if it's wrong!!!😆

I think the clue here is that the clock reset to 12:00. Since the clock doesn't rely on any sensors or external input, it's clear that whatever module the clock "lives in" is losing power, or otherwise resetting itself. I don't have access to my manual, but I think that the clock circuitry lives on the instrument cluster module. Anything that interrupts power to that module (battery cable, battery clamp, fuse, connector, cable, or a myriad of other possibilities) could cause this kind of problem. If you notice that the clock seems to reset when you try to start the car, I'd look at the battery clamp and cable (including the ground side), as a weak connection there might be invisible until you try to draw starter (high) current through it.

Thank you for that. I'll check the terminals.

You can also pull the entire cluster from the dash. The cluster has an interesting wiring method. The female part is in the cluster. The male wiring part is attached to a metal bar that allows it to slide left or right to align with the female part of the cluster. Once you align the male part you forcefully seat the cluster so that the wiring connection is made.

Maybe someone before you has removed the cluster and not seated it properly or maybe the cluster connection is corroded, who knows. You can also replace the cluster lights while you are there. Maybe some nice LEDs.

I had been rolling that very idea around in my head, the more I do, the more I agree with that theory of someone golden screwdriver. And LED's would be nice. I'm gonna replace the headlights with LED's. Thank for you input. While I'll here, there's this fuel gauge issue I have. The fuel gauge didn't work, so I replaced the fuel pump assembly, and it still doesn't work. Occasionally it'll read a half tank, but that's usually right after I fill it up. Think maybe this could be related to the instrument cluster? The only thing is, it's random and inconsistent with the symptoms.