Rsmonty, Don't get so discouraged! <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> Remember that these are old vehicles, and stuff happens.

Please give some details about where you are located, and more about the truck so the guys here can better help you.

Don't worry we're all happy to help as much as we can and most of us have been there before so we know where you're coming from.

Also, do let us know where you're located. In many cases, if someone is near you, they're usually willing to swing buy and help if you ask.

Ray <img src="/forums/images/graemlins/kewl.gif" alt="" />

Well, to me that sounds like a bad ECM. That's supposed to be the first indicator of trouble - if you're not getting the a-okay signal from the unit (continuous long sweeps, or in your case with the digital unit, repeated rise and fall readings) then I would think it is safe to say that the computer is toast. Just my 2ó...

That is a bad ECM/ECU (Engine Control Module/Engine Control Unit). A good one as was said will pulse regularly.

Here's the ECU code chart...

Yes follow what frank said. However when testing primary resistance which is under 1 ohm, it is imperative that you zero the meter with the leads connected together before testing as the meter leads will add to the actual resistance and give you a false reading.
Conner

Thanks guys. I'm in South Jersey. I'm not quite ready to call in the calvary just yet. I really appreciate all your feedback. I have just enough brain to WANT to try to fix it, yet not enough smarts to do it quickly or even right!
Had a wicked thunderstorm last night and was unable to do any work. Maybe I should have done a rain dance around the truck in hopes of sparing the ECM. Will get back to you with my next bumbling attempts. <img src="/forums/images/graemlins/smile.gif" alt="" />

Ok, here are some values I got: As per FrankR's direction,
My reading was 1 ohm.

I got 12K ohms.

Doing this test exactly as Frank suggested, my reading was 694 ohms.

I got no continuity.
If this test is valid for a '91, I may have a bad power transitor as Frank suggested. I will try to order one from dealer. Interestingly, I called a local junk yard just to see if by chance they had any Mitsubishi's in stock and the guy told me that an Egyptian guy buys them up the minute they get them in. Hmmm. <img src="/forums/images/graemlins/mrt.gif" alt="" /> I will also check on pricing of an ECM. My reading indicated it was toast.

Good work <img src="/forums/images/graemlins/kewl.gif" alt="" />

The coil is close enough for horeshoes and hand grenades. I think the power transistor is bad. Before you condemn the ECU, try to find a used coil pack with the transistor and see what happens because - though I'm not certain - a failed transistor could possibly cause the ECU to read bad. Perhaps someone else knows if that's possible.

Someone recently found a power transistor at Advance Auto or one of the parts houses, but I don't remember if it was expensive - or if it was the correct replacement.

Try carpart You'll have to choose one and call - ask for the coil and make sure the entire assembly is included.

Hopefully someone here will have a spare unit you can buy.

Good luck,
Frank

Yeah, that was me. But did you remember that I was performing the test wrong - it was supposed to be tested while still on the vehicle, not off like I did. The PT I found was at a Murray's - went for something like $40 IIRC. But my problem ended up being an intermittently shorting out coil.

G'luck...

Shawn

Ugh. I did the test wrong too. I also removed the power transitor to work on it. <img src="/forums/images/graemlins/frown.gif" alt="" />

One step forward, two back...

I guess I can stop patting myself on the back and see if my foot can kick my rear.