ECU...

Did it run ok after you started it or are there still signs of problems?


You're looking for 12v so you may want to go to a higher multimeter setting.
[/quote]so when I went back to grab the codes the same issue occurred: the check engine light won't turn on.

It won't go into self-check and the voltmeter is no longer picking up any activity.

Edit: Ok a few hours later and the Check Engine Light still won't appear, and I unplugged the battery with no luck either. And as expected no activity monitored from the diagnostic pins.[/quote]
When you say the same thing happen, do you mean it won't start/run? If so, then definitely pull your ECU and check for burnt components or leaking capacitor (cylindrical components). The leaking fluid is an acid that will eat your ecu board destroying it.
Also check if your idle speed controller is within spec since a bad one can destroy your ecu.

A bit rich, but no other problem were detected.

When the Check Engine light does appear it starts up as normal, and I can get some activity at the diagnostic terminals, but they make no sense: When I to 50V it just made identical sweeps, rather than some longer and shorter ones. Repeating itself up to 60 times. At a lower setting, 10 I think, it will do equally non-nonsensical things like make 70+ whole full sweeps without pause.



I'm still inclined to believe it is the ECU. Will the guys at AVPro test/diagnose a faulty ECU before repairing it? Because all I can think of to isolate the issue is to get another 'known' ecu to remove that variable. (And with the most inexpensive replacements being over a 1/3 of what AVpro charges I find it rather difficult to justify and would rather send it to AVPro to get refurbished given their reputation around here.)



Indeed. It will just turn over but won't turn on when the Check Engine Light doesn't go into self-check when the ignition is set to ON at start up. However, when it does turn on it starts up and runs as normal.

I pulled the ECU and opened it but didn't smell anything particularly foul as had been mentioned in previous threads. The capacitor at C105 appears to have some corrosion on it, or crust/debris underneath it. It also has a pin-size hole and some scuffs around this hole. (An indication of a leak?)



Will do.

Ahh... just my luck. Link is down.

http://www.montypics.com/pic.php?url=/off-roader/2002-06-18/isc_servo2.jpg

Do you still have the originals? I removed the intake off the TB and saw a brown connection, and proceeded to clean the two componets after disconnecting it in an attempt to see a change in the idle, but the Check Engine Light didn't turn on and I decided I'm done for the day. But I look forward to seeing those images of your walk-through.

Thanks, guys! <img src="/forums/images/graemlins/kewl.gif" alt="" />

The sweep pattern you describe is no codes stored and ecu functioning ok.

In the words of Bill, the drunken a&p who taught me a lot of what I know, 90% of all problems are electrical. The other 50% are stupidity.

If you have a holed cap, send it off. You have an intermittent fault, probably a trace almost eaten thru on the circuit board.

Or, a quick search of car-part.com has used ecu's for your model for from 150 to 350 bucks. Rebuilt sounds better to me. One other possibility is a failing ecu relay.

Eddy, you're right. After doing my due diligence and price checking it was certainly on my to-do-list. That is until I cleaned up the 3 screw brown clip casing, thought to be the Idle Speed control--its located under the TB and the intake, it has a spinning disk at the end of it when you remove the exterior pig tail clip--and the black clip adjacent to the ISC on the Throttle body.

It made a difference as it stabled the idle from 1500 down to 1000 when in Park and a warm engine.

This was short-lived, however. After a few time shutting it on/off it caused the same issue, Check engine light was missing, it wouldn't turn on etc... So my next thought was to wait until the next day, but unplug the clip going to the ISC. And well, the ECU turned on every time I tried and ran steady as it did when I cleaned top and middle part of the ISC.

I think I'm dealing with the early stages of an ISC destroying the ECU. As I said, their was a pin-sized hole in the capacitor so its on my to-do list. But I'm going to see what happens and see what's the deal with this ISC.

Thanks for the help so far, guys. Keep it coming!

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

EDIT: ISC id confirmed.

http://www.4x4wire.com/mitsubishi/tech/throttle_body/