95 Mitsubishi Expo - mechanic unable to fix check engine light


I’ve owned my beloved 95 Mitsubishi Expo since 2004 - and in all that time the check engine light has been on most of the time (except when the battery’s been unplugged and it goes off temporarily). In California, a car cannot pass smog with a check engine light on (even though my car handily passes the emissions test every time) and until this year I’ve been able to pass ‘under the radar’ without fixing the check engine light (I did try to fix it a couple of times, with no results, so gave up). However this year the DMV is really cracking down and I can’t get my smog certificate/registration (and I’m way overdue now) without actually finally fixing that check engine light. The problem is - no one can fix it. I’ve had several mechanics try. Different codes have come up, and I’ve had the parts/sensors replaced. Finally, the code that is reading now is “camshaft sensor.” My incredibly nice mechanic (who’s been trying to fix it for free now, after I spent a bunch of money there) replaced the entire distributor (in which the camshaft sensor resides), but the car is still coding. My mechanic thinks the only thing l can do now is replace the car computer; I’m on the lookout for another Expo with the same computer (has to be CA 2-wheel drive), but I understand they are extremely rare. I’ve shipped my car’s ECU to a foreign auto ECU repair place in TX. So far they have not found anything wrong with the computer but they’re looking again.

Is there anything else my mechanic should be checking for? Wiring/electrical issues? Should I take it to some kind of specialist perhaps?

I’d really really like to keep this car - there’s so much good useable car there! it still runs great, gets good mileage, is extremely comfortable and does/carries everything (and everyone - for group camping outings, etc) I need!

Thanks for any help!! You’re my last hope!

Hi - actually I think the code is “cam sensor” (Is that the same as camshaft sensor?). Anyhoo, I sure hope someone out there in Cartalk land can help! Thanks!!

WHICH "cam sensor code?

  • DTC P0339 Crankshaft Position (CKP) Sensor Circuit Intermittent
    • DTC P0340 Camshaft Position (CMP) Sensor Circuit
    • DTC P0341 Camshaft Position (CMP) Sensor Performance
    • DTC P0342 Camshaft Position Sensor Circuit Low Input
    • DTC P0343 Camshaft Position Sensor Circuit High Input
    • DTC P0344 Camshaft Position Sensor Circuit Intermittent
      something else?

What were the other codes?

Any of these should cause operating problems. Do you have any?

Do you know the code? There are cam sensors and crank sensors on your car. Cam sensor failure could be timing off. Was the timing belt replaced and if so has he checked to see the timing marks still line up?

Thanks for your reply! It’s definitely the cam sensor not crank sensor. The timing belt has been replaced and my mechanic has been trying different things with the timing - to no avail (that’s why he thinks it’s a computer issue). Though I’ve read online that wiring/electrical issues can also cause a false code. If you have any other ideas - I’d love to hear them!

I’ll call my mechanic and find out which code it is and let you know. Thanks!

It’s PO340 Camshaft Position Sensor. The car runs fine, so it appears to be some kind of false reading. I hope that info is helpful. Let me know if there’s anything else I can find out.

Oops, typo, that’s P0340 (typed an “o” instead of a zero). Thanks again for any help!


I suggest you find a mechanic that will have the patience and ability to diagnose your car using the genuine Mitsubishi service manuals and wiring diagrams.

Thanks db4690. If installing a replacement used computer doesn’t do the trick, I plan to take it to the Mitsubishi dealer. The mechanic there says they’re used to working on older models.

If anyone’s had any experience with this sort of thing - I’m still open to suggestions. Thanks!

I have a '94 Expo in CA and really like it, though I had rust spots on the roof.

My Expo squeaked past the smog check a few months ago and had issues with that light. A lawyer neighbor registers his sports car in Nevada - maybe that’s an option !


California DMV is getting wise to that.

A colleague recently got busted. DMV was able to prove that his cars spent all their time in California, not Nevada.