Thread: How or when ECU goes bad?

I'm troubleshooting an AAC issue. It ticks and continues ticking with the key in off position.

When I remove the proper fuse and put it back, it stops ticking.

I measured 8 Volts on the AAC connector.

I'm wondering if this could be the ECU and I also would like to inform about ECU problems in general, can a bad cabletree blow up something in the ECU? Something that the AAC still works but ticks?

Or that car starts and runs fine but Datascan or another ECU program hangs on it or only shows 4 bars with 3 no clarifcation what the bar is showing and the 4th bar is water temp but it moves like it is injector?

How real is the idea ECU just went bad on some little logic inside but the rest seems to work?

I tried another AAC, also starts ticking after complete shutdown.

The 8 Volts I measured, is with ignition off. Same car without ticking gave 0 Volt.

There are no other issues, what I mentioned about not being able to read the ECU, is another car.

Anyone here can tell me anything about broken ECU's within a running car?

have you tried another ecu ?

ive had two broken ecus one would refuse to send tach signal, and the other i forgot what it did lol.

stratton.

I didn't try another ECU yet, I have '93 SR20DE with the electrical speed sensor. It's part number is different from the '90 - '92 SR20DE with the speed sensor with cable.

I couldn't find out beforehand if it wouldn't hurt something in the car if I tried the older ECU. However still not sure about this, I also can't think of a reason why it would fry something in the car.

I'm getting another ECU, this time with the right part number (23710-71Y05)

I figured that the only part that is getting power with ignition off is the ECU. So when I measure 8 Volts on the AAC connector, it must be comming from the ECU. I ruled out a lot of wires besides that tricky part between the AAC and the ECU. This is because I don't really know how to do this and besides pulling a fuse (electronics B) but it's called different in FSM, left bar, 3rd from under. However this one hooks up the AAC for a SR20DE with the battery.

Then I went to the last page in FSM, that huge drawing that is so readable and it's really Japanese drawing, because they actually hooked up different wiringlooms for different engines and then I found that one wire from the ECU goes to the ''air regulator'' which must be the AAC and that same wire is hooked up with the fuel pump. :S

Then again, when I puel the fuel pump relay clicking also stops and doesn't come back when I put that relay back.

But I'm lost on what step is best to take next to solve this issue or to pin point the faulty part.

You can use the earlier ECU no problem, you can also use a '94. The speed sensor works the same at the ecu for both.

In the earlier cars the speedometer generates the signal to the ECU. In the later cars the speedometer conditions the signal from the speed sensor before it goes to the ECU. My '93 has had '91, '93 and '94 ECUs in it and all worked fine.

Note: this is all US stuff, the euro parts may be different.

Ok you, Vadim and a Dutch racetrack dude I bought a Whiteline swaybar and the ECU with the correct part number from, convinced me. I'll try the old ECU first and for this time, I hope it is the ECU, since I already sold the engine loom.

That spare battery I carry with me all day has to go.

my old ecu would have me running pig rich

fire out muffler type sh1t

I'm stumped.

I had the ticking AAC for months, tried everything besides measuring on the ECU connector and I pulled all fuses (again) but this time I went drinking a couple of beers till I put them back. Of course I had already tried to reset the ECU.

Without checking if the ticking was gone, I could notice the ECU was resetted. With cold starts, now the idle goes up and down 3 times (or engine just dies because the idle went down to fast the first time), so I figured that the ECU needed to be put in timing mode once, faking a manual adjustment of idle and timing. But that didn't help either for the weird idle on cold start.

However, I noticed a battery voltage of 12 Volts instead of the usual 10.8 Volts. At that time that didn't ring a bell but today I wanted to pull the ECU out, but first I checked for the ticking of the AAC.

It was silent. I measured the current draw and my multimeter is kind of crappy but with the ticking it was 0.6 Amps and now it kept telling me it was 0.003 Amps, which is kinda next to nothing.

Then I disconnected the AAC and hooked the connector on another AAC, started engine, wouldn't *idle* at all, I shut it down and check if that AAC might be clicking. It wasn't clicking.

So now I dunno anymore wtf happened but the ECU doesn't seem to learn to idle with cold starts, it revs up and down, sometimes shuts down but usually tries 3 revs and then it stays idling. Car drives a bit harsh, which it didn't do before.

So the ticking is gone, I didn't replace ECU, with diagnosing the AAC I can see it works fine but instead a cold start issue for no reason.

What step should I take next?

p.s. This also tells me there is a difference in resetting the ECU and leave it starving for battery. Makes no sense to me.