420A Pretty sure my ECM is dead...

Dalton63841 · Jul 28, 2015

I have a 1995 Talon 420A 5 speed. (Yea, I know, should've gotten a 4G63) I've searchedon multiple forums and google and frankly I'm tearing my hair out because symptoms are weird, but I think it's a dead ECM.

So last night, I drove to the store, and she drove like a brand new car, as usual... Then when I got back into the car to leave, I was stuck in a "crank but no start" situation... When I turned the key on, the tach went crazy jumping around, and a few random dash lights blinked. After a while I was able to get it started by padding the gas pedal and limping it home, doing my best to keep the RPM's up or she would die. Today, I checked out electrical connections, cleared off corrosion, and reset the ECU by leaving the battery terminals off for about 30 minutes. After that she drove great for about 20 minutes, but then the CEL came on, and she died. Now, any time the key is in the switch, the tach jumps all over the place, but the CEL does not come on with the key(my clue about the ECM), and she won't start.

Sorry it's a bit wordy, but I want to be thorough, as anything might be the clue to the answer.

EDIT: Just remembered another small thing, but should the ECU be getting VERY hot? Not engine hot, but surprisingly hot.

wolf alchemy · Jul 30, 2015

It could be you collant temp sensor. That's what mine did. Spent 30 mins at auto zone going through the three DSM models and a lot of car years. XD not fun.

Dalton63841 · Jul 30, 2015

wolf alchemy said:
It could be you collant temp sensor. That's what mine did. Spent 30 mins at auto zone going through the three DSM models and a lot of car years. XD not fun.

Okay, shameful post here... Mere days ago, I replaced my thermostat, and forgot to tighten the hose clamp for like a day. When I saw it starting to get warm, I found the loose clamp, tightened it, and topped up the coolant. It never overheated, but it did leak coolant.

If I remember correctly, the coolant temp sensor is immediately under that hose where it connects to the thermostat gooseneck so probably got a good soaking... Seems likely that could be a problem.

wolf alchemy · Jul 30, 2015

Hey. Nothing shameful. We've all had our fails. I put a donut tire on a mustang and drove 30 miles. Got home and went to check it. Only two lugs were holding it on. I was lucky the other three didn't fall off. Oddly I put enormous torque on the lugs. =/

o0GuitarKid0o · Jul 30, 2015

You should get a logger obd2 tells you alot more than say my laser with obd1 ,

Since this is 420a ( I've never worked on one) it may not apply ,

but things I'd check would be idle speed controller give that a look, and if your cars has an idle position sensor (I no 1gs have one) , leaks in the throttle body

*give your throttle plate a cleaning it may have some carbon build up witch caused the throttle plate to Stick and not seal properly that one time and possibly more times in the future ,

Other than that I think someone with more experience with the 420a platform should chime in although I can deffinitaly try my best to help ya

Dalton63841 · Jul 30, 2015

o0GuitarKid0o said:
You should get a logger obd2 tells you alot more than say my laser with obd1 ,

Since this is 420a ( I've never worked on one) it may not apply ,

but things I'd check would be idle speed controller give that a look, and if your cars has an idle position sensor (I no 1gs have one) , leaks in the throttle body

*give your throttle plate a cleaning it may have some carbon build up witch caused the throttle plate to Stick and not seal properly that one time and possibly more times in the future ,

Other than that I think someone with more experience with the 420a platform should chime in although I can deffinitaly try my best to help ya

Oh yea I am just waiting until I get a bit of gas money to continue further testing. I've been meaning to pick up a bluetooth OBD2 module, so I guess this is as good an excuse as any to do so.

Here in a few days when it's less miserable, I'm going to check out the coolant temp sensor and the idle air control valve... Would RP Max-Clean take care of deposits in the throttle body, or is this something I should remove the throttle body for?

o0GuitarKid0o · Jul 30, 2015

Dalton63841 said:
Oh yea I am just waiting until I get a bit of gas money to continue further testing. I've been meaning to pick up a bluetooth OBD2 module, so I guess this is as good an excuse as any to do so.

Here in a few days when it's less miserable, I'm going to check out the coolant temp sensor and the idle air control valve... Would RP Max-Clean take care of deposits in the throttle body, or is this something I should remove the throttle body for?

Ahh I see,
deffinitaly get a logger it never hurts to know what's going on.
I used carb cleaner for cleaning my throttle body while it was still attached,
I presume you could get a better cleaning if you removed it and at that point you might as well replace the gasket

Dalton63841 · Aug 6, 2015

Update: My car seems to be consistently running smoothly now. I've driven it several miles and it stays running and starts every time.

HOWEVER, my CEL came back on. I did the key dance and I get 12,11,55, which seems to indicate a lack of signal from the CKP. I also read the OBDII and it is showing the P1390, which seems to indicate a skipped tooth on the timing. That would be odd though. I just had the timing done a month ago.

The ONLY symptom my car is showing is an odd high idle. I can start it and it idles at 950(fine), but after driving it a few miles, it will start idling at over 2000.

Any ideas?

o0GuitarKid0o · Aug 6, 2015

Isn't engine light 12 the thottle position sensor? That has your idle switch and if faulty your car won't no your off throttle it's pin 3 ,

Check continuity between pin 3 and 4 closed throttle, when you lift a the pedal it won't have continuity till you close it again,

Dalton63841 · Aug 6, 2015

o0GuitarKid0o said:
Isn't engine light 12 the thottle position sensor? That has your idle switch and if faulty your car won't no your off throttle it's pin 3 ,

Check continuity between pin 3 and 4 closed throttle, when you lift a the pedal it won't have continuity till you close it again,

Oh I must have misunderstood something. It was my understanding that the 12 was the beginning, and 55 was the ending, and you watched what was between those two.

Okay Im not too sure how to do this... I supposed I need the car running, and check that pin while revving the car up?

o0GuitarKid0o · Aug 6, 2015

my mistake I'm thinking of tcu codes, that would be mas , unless your right I'm going off 1g knowledge so maybe it goes 12, (**),55

The Top DSM Community on the Web

420A Pretty sure my ECM is dead...

Dalton63841

wolf alchemy

Dalton63841

wolf alchemy

o0GuitarKid0o

Dalton63841

o0GuitarKid0o

Dalton63841

o0GuitarKid0o

Dalton63841

o0GuitarKid0o

Similar threads

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds