Ppags

So I've been battling this electrical gremlin for quite some time now.. The PCM reads "No Comm" when I try to read codes with the on board system, as well as a handheld scanner. Anyway, after months and months of trouble shooting I've come down to this.. The only time I can get the pcm to actually work and have comm is when I unplug any 1 of the injectors. I plug it back it, immediately no comm. What could be causing this? Do all the injector grounds combine into 1 wire, and then go into the pcm? Or do they each have a ground going into the pcm? That's really the only thing I can think of that could be causing that to happen

dadaroo

I answered that for you before. Each injector has a separate ground wire going into the PCM. The injectors are always powered when the ignition is ON or in START. The PCM grounds each injector in sequence to activate them.

I am still waiting on you to tell me if the car will run when you have one injector disconnected.

Ppags

Yea sorry about that, the mechanic who was working on it is still on vacation till monday, so I can't get ahold of him until then. But I'm getting the car towed back to my house tomorrow so I'll definitely have an answer for you then

dadaroo

10-4. The PCM No Comm issue has me stumped. I wish that 2nd PCM had been a good one. You previously mentioned you were going to send your PCM off to see if it is the issue. Cardone is one along with NEC and some others.

Ppags

Yea I found a guy on eBay that had great reviews and spoke with him, he said he could at least try to pull the tune off it and save it to eliminate that headache if the pcm goes completely, as well as try to see what's wrong with it. But I want to try to find someone local to bring it to. I'm not a big fan of sending things like that through the mail.

Ppags

I guess I should also say that I'm currently in the market for a 98 pcm if anyone knows where I can get one for a reasonable price

Ppags

So I'm looking at the pin outs on my PCM, here's the link: http://corvetteforum.shelor.net/Corv...tor_Pinout.htm

on the red connector what injector wires are the ground? anybody happen to know?

4DRUSH

The ones that say 'Injector Control'

Ppags

Woooow. I completely misread the diagram. I was reading "ignition control" as injector control, and was wondering why in the hell is there 16 injector control pins? Well played sir

Ppags

Well I got the car back, but the battery is completely dead and most likely frozen bc it's only 20 outside, and was left on the truck overnight. So it needs some time to warm up before I can try to charge it. The garage said they put in the new ignition switch I sent to them, but it's still new in the box sitting on my seat so I dunno what the hell was going on with them, so I guess that could still be my problem, and they only put 3 lug nuts back on my damn passenger wheel, and left the wheel well hanging by 1 screw. Exactly why I hate having other people touching my cars

dadaroo

I don't think your ignition switch is your issue. You can put it in or we can just check voltages at the fuses it feeds to confirm if it is bad.

Please disconnect your dead battery if you charge it in the car. I can explain later about square DC waves and electronics.

Sorry about the shop issues.

Ppags

Yea it happens I guess. The battery is still on the trickle charger going on 24 hrs now. It was completely drained. Im gonna mess with the car tonight once my daughter goes to sleep, maybe I'll get lucky

dadaroo

If you charge a dead battery in the car DISCONNECT the negative cable first. Normal car chargers produce DC square waves that can pound the electronics and damage them. A really dead battery cannot filter these. If a battery is just a little low there is no concern.

Ppags

The battery is completely out of the car sitting on the shelf while it's charging. I checked on it earlier and I think my charger fried overnight. It won't turn on anymore. Can't catch a break with anything lol

Ppags

Battery is still charging on my little 8 amp charger. I don't think it should take this long though, I was thinking 10 hrs or so charge time. So I might need another battery, if so I'm gonna go with an optima I think. Yesterday I had a little time and took the pcm out and checked all the pinouts. There was a little sand in the red connector, so I cleaned it out. Didn't find anything else wrong, rechecked all the grounds, and put the new ignition switch in as well. Guess we'll see what happens when I have a good battery to put in.

BigGun

Why don't you just run it down the parts store and have it checked? Most do it for free. Bet that battery is toast. There are many good batteries out there that a much better value than optima(imo).

benspeeder

Hi this is interesting and new to me. How does this damage the electronics? I recently charged a totally dead battery in my Z06 and ultimately replaced the battery only to find the dreaded abs/tcs/no com messages. Running a thread already on that situation

Cheers!

Ppags

Battery is charged,I did have it tested last night to be safe. I put it in real quick this morning before leaving for work, same problems, no comm, reduced engine power. I didn't have time to pull the injectors to see if it ran, I'll do that later. I did notice when I tried to roll the Windows down, that I couldn't control the passanger window from my driver side panel. and the memory for the seat doesn't work anymore. If the pcm is really the problem, would it cause the bcm malfunction as well since they are all tied together?

dadaroo

Let's take a simple battery charger using 60 cycle AC and converts it to DC and does it using the Full Wave conversion and produces 60 square waves and not 30. This is like turning the electronics on and off 60 times a second when a battery can't help filter or mitigate this condition.

You may ask yourself then why does my computer power supply not damage the electronics? Good question. It is because the power supply is much more complex and actually makes a virtual true DC current. At least as close as possible.

Mr. Sam P. E.

Ppags

I just tried disconnecting each injector, but couldn't duplicate the results the shop had. Still getting the no comm, reduced engine power, low feul messages.