Please read!! Possible Ecu problem

Shane Reber

Asked by Feb 22, 2016 at 07:55 PM about the 1990 Mitsubishi Eclipse GS 2.0

Question type: Maintenance & Repair

I put a good used alternator on my car and used
the negative terminal test and it worked then after
5 minutes of running with all the accessories on it
died and the alternator was dead. The next day I
bought a new one put it on there and used the
same test. But it ran again without the cable on
there so I thought it was a fluke cause it worked for
3 days. But the other day everything started getting
dim like a bad alt and it ended up dieing. I got the
battery and alt checked they were both fine. My
terminals are clean and look good and so do the
wires could I have fried an Ecu fuse or something
that easy?? I know nothing about Ecu computers.

12 Answers

Shane Reber

Honestly what's the actual odds


Did you remove,clean and re attach the negative battery cable from the frame and motor? These cars are known for your kind of issue with these connections not be repaired after years of driving. I feel your ecu is probably ok. That being said the old school way of testing an alternator by removing a battery cable is very dangerous on newer cars. If can fry electronics. But normally if this happens the car would not crank at all even with a good battery.

Best Answer
Shane Reber

Ohhh I see. And what does the one that goes to the motor look like. Is it a bolt or is it like a plug. And how would I go about getting it cleaned cause the line runs down under dome stuff. But it's really black and sludge down there.


It should be a bolt thru a ring lug on the cable. Follow cable from battery and you will find both. Just remove the bolts and wire brush the ring lugs and the surface it hooks to on the frame and motor. Remember to unhook both battery connections before you start, also inspect the cables at the battery. If there is any frayed wires sticking out then also repair these too

Shane Reber

The ground connected to the motor is in a really bad spot. I don't know what to take off to get to Ithe it's uner the ecI multi thing where the throttle is down under all that.

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Shane Reber

So whats the easiest thing to disconnect to get to the ground on the motor


Not sure in your case without looking at it. Long extensions may help you get a socket on it.

Shane Reber

Can a faulty fuel injector do the same thing? Because my lights started getting dimmer and dimmer and when I try to accelerate over 10mph it would start to stall. Can it be a eci relay?


Lights getting dimmer leads me to believe that it's in your charging system. Nothing much else would cause your battery to go dead. If alternator and battery are new then I would clean all connections.


Ok charge battery then do this test. With car running use a multi meter and check voltage at the battery. You should have 14.5 volts with car running. If you do and battery still going dead while driving then it's battery cable connection issues either on positive side or whole negative cable side(battery,frame or motor)If you have less than that then check from positive of battery to any metal on the motor. If you have 14.5 or so volts now then it's a negative cable connection issue. If you have less now test the alternator straight to the motor. If you have 14.5 or so volts now then it's a connection issue in the harness from alternator to battery or positive battery connection issue.

Shane Reber

The car wouldnt run. After the night I couldn't get it to start anymore I took the alt and the battery in and they were fine. Car isn't back together yet because I don't want to put the alternator in and put it in wrong.

Shane Reber

And I'm visually checking other things. I don't have anything to test connections with

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