I scratch my head at that if all eight injectors were firing according to the NOID light.

What that does tell us is that crank signal is good (that's where the ECU gets the timing to fire the injectors), and ASD is firing (or you wouldn't have 12V to fire the injector.)

I hate to say it, but at this point, I'd be hunting up a compatible ECU and swapping it in.

92/93 should swap in.

RwP

 

I'm thoroughly baffled too Ralph. How can a noid test say the ECM signal is fine but my OBD1 code 27 say it is NOT fine??

Went back out just now to fire up the truck. No go. Tried twice to start up up and it wouldn't fire. I had the hood open just to see how the ECM mounted so just for fun I took my pocket knife out and tapped all around the ECM. Tried starting it again and it fired up. Coincidence? Who knows!! But I can say after turning engine off and on a couple more times and then parking it back in my garage I decided to see if I was still getting the Code 27. Sure enough, I am. The engine light is not illuminated but that code keeps coming up when I cycle the ignition three times.

At this point it seems my only option is to swap out the ECM. What can it hurt? I understand the 1993 ECMs are a simple swap out plug n play so I don't have to worry about VINs or the like. Any suggestions as best place to get a refurb? I have an Advanced Auto with one in stock. It's a Cardone but the three reviews said it sucked.

 

Cardone really doesn't have a very good reputation when it comes to their 'reman' parts...... I went thru two power steering pumps before I gave up on them, (neither one put out any pressure at all.) and bought another brand. (laird?) See if one of your local junkyards has one laying around you can pick up cheap. Or, if Cardone is all that's available, buy it, do NOT give them your core..... try it. If it works, take your dead one back. If it doesn't, return it, and get your money back.

 

Tapping brought it back?

Hrm ...

I'd consider carefully tightening the females on the connector first; dive into the factory service manual on how to remove a connector from the housing at the PCM, squeeze it a bit, and then reinstall it for all the connections.

It could just be a bad solder joint (cracked with age) in the ECU; but since it's got a conformal coating, you can't just open it up and touch up all the solder joints, alas.

RwP

 

That was my thought...hang on to my ECM until I know the replacement works. I'd hate to turn mine in and have the replacement be a POS. Then I'm up a creek. Boneyard is an option too. Thanks!

Looks like that connector comes off easily. Just a bolt it the middle. Not sure I know what you mean by "squeeze it a bit".

 

BTW, once I have that connector off is there any problem with cleaning the plugs with contact cleaner?

 

Nope. It's actually a good idea.

 

Inside each hole is a connector; I mean to pull each one, tighten it up, and put it back in.

Again, check into the FSM (first pages of the wiring diagrams!) to see how to do this.

RwP

 

OK, I think I found it in the 1995 Service Manual on Page 8W-01-7. It shows what appears to be the connector I'm going to be working on for the ECM. It calls for a special tool from special tool kit #6680. WTH??? Where do I get that special tool kit? Or is that overkill and I can use something else?

 

Amazon. They are called 'de-pinning' tools.