I have a 94 Turbo that had a bad engine computer, and after replacing it, it worked about a year. I was doing a bunch of preventive maintenance, and one day it wouldn't start. It seems I have a bad one again.

The symptoms are the exact same as the first time. No spark, crank and cam sensors are good, have voltage to the coil, but the (-) side never gets triggered. Here's the weird part - if I hook up the diagnositic pigtail to slow A2, the LED glows, and it won't go into diagnostic mode. This was exactly the same situation as the first time. I posted that here, nobody said anything.

So now that it's happened twice, I have some simple questions:

1. Did I do something to mess this up? Are these things "fragile"? If somebody needs to say "oh, they always go bad when you install them with the headlights on" then please let me know.

2. Has anybody here had a problem where the same car killed more than one? What was the problem?

3. Does anybody repair them?

I have two volvos, but the other one is not a turbo, so I can't swap.

 

Here is my better description from last year:

https://volvoforums.com/forum/volvo-...o-start-63711/

Junkyard ECM fixed it right up, ran great, now I have the same symptoms.

 

Best suggestion I have is check all your ground straps. Clean the surfaces up and replace any that are damaged (good time to upgrade to a heavier duty strap as well )

Modern cars tend to be finicky about power and ground, and from what I understand, more so with these Volvos (everything is ground switched on them from what I can tell, much like Subarus).

It also sounds as if it could be a wiring issue somewhere as well. I'd suggest checking the wiring to the ECU also

 

I thought about pulling the whole harness off, having a look at it, and putting it back on. That sounds awful, but it's really not that big of a job. The way it's packaged on the passenger's side, I can't really imagine getting a look at it any other way.

 

Give it a go, whats the worst that could happen At least its something you can rule out :thumbsup:

 

I'm thinking it's a wiring problem.

Having an ECM fail is rare but having two go ... If it was a new one I'd say it's near impossible but I'm guessing you pulled a used one ?? Even used it's pretty unlikely and more probable it's something taking it out.

Might be something in the wiring shorting out and causing them to fail. Other thing is to make sure it can get air through the ducting so it has something to cool it.

 

Anybody know where ECM ground connections would be?

 

Okay, I figured it out! The connector for the "main relay" mounted above the radiatior deteriorated, and when it drops out, you can have a no spark condition with the LED glowing dimly when connected for diagnostic codes. Obviously, if I had checked the voltage on the circuit from this relay (it goes everywhere) I would have known it dropped out, but I was looking at ignition components instead. Not great troubleshooting on my part. On the bright side, I have some spare ECM's now (they're all good) Ha ha.

David Barton sells the parts for this style connector, but of course his site is focused on older rear drive volvos. I am going to update my other thread as well, for posterity.