kimmer

Ok I have the 12 volts on the grey but nothing on the black so this is an open between the two.

FrankieD

Alright , that's great that you confirmed 12 v is on the Grey Connector.
Now the only way this 12v gets transferred to the Black Connector is when you plug the Grey and the Black Connectors onto the Coil. The Coil's Primary is Internally Connected together to allow this to happen.
So now if you do not measure 12v on the Black Connector when they are plugged onto the Coil is because the Coil is bad. This is what feeds the 12v to the Ignition Control Module on Pins A & D.

Now in order to verify that the Coil's Primary is ok is to use an Ohmmeter and check for resistance. The Coil's Primary has 4 pins(2 for the Grey Connector and 2 for the Black Connector) They are all internally connected together. Now if you do ANY combination of Ohmmeter check on any combination of these 4 Primary Coil Pins they should all measure Zero. This is how you have to verify if your Coil Primary is good. If any of these combinations is not Zero then your Coil is bad.. this is my suspect from the beginning..even a new Coil can be bad.

Sidney004

This is a great technical forum!

kimmer

Ok Frankie, I checked it and came out with 2 ohms all around. But I also checked 2 other coils I have with at least one of them known to be good [ I believe] and they both measure the same. Are you sure about this because if there is a connection there will always be some resistance, am I correct? Can I back probe the black connector? [ it doesn't look like it] Would checking the continuity of the coil pins work? I did try it but didn't get any beep. Bty I really appreciate your help.

John Robinson

Try getting out of the box your in and look at this box. The TPS sends signals to the ECM about throttle openings etc. And the signal goes through the ground wire. Bad or confusing signal to the ECM and it will hunt and peck the other sensors trying to make the engine run. If it gets a faulty signal that it thinks (for example) the engine is flooded because the TPS has a broken wire or ground then it will shut down the fuel until it sees the engine is running.

kimmer

My problem is a no spark so thats not it but thanks for your input.

FrankieD

Your 2 ohms resistance measurement of the Coil primary is Ok.
Lets now prove that the 12v from the Grey Coil connector is making its way to the Black Coil Connector through the primary Coil. Plug the Grey coil connector into the coil but leave the Back Coil connector unplugged. With the ignition turned on measure the voltage on the 2 pins of the Coil where the black Coil connector would go onto. If you have 12v there that proves that the Coil primary is good.
If this step is successful then its time to plug the black coil connector onto the coil and taking voltage reading with the ignition on to Pins A & D of the Ignition Control module. These 2 pins should both read 12v. If you do get 12v on Pins A&D then I would suspect a faulty Ignition Control Module.
If you do NOT get 12v on pins A&D of the ignition Control Module then we have to prove the wiring is good from the Black Coil Connector forward towards the Ignition Control Module Connector.We do this by leaving the Black Coil Connector on but unplugging the Ignition Control Module Connector. Now with the ignition turned on you should read 12v on the Ignition Control Connector pins A&D. If you do get 12v on these pins A&D then the wiring is Ok from the Black Coil connector to the Ignition Control Module Connector.

kimmer

Ok, got my 12v from the coil on the black connector side, on the icm connector A is .47 & D is 0. The FSM states it would be a faulty coil connection or a faulty circuit from terminal to coil.

FrankieD

OK now lets verify that the wire from the Black Coil Connector to the ICM Connector is good and not broken.
We do this by checking the resistance of the wire using an ohmmeter.
With both the Black Coil Connector and the ICM connector unplugged test with the ohmmeter for Zero resistance from the Pink/Black terminal of the Black Coil Conector to Ternminal A (Pink/Black wire) of the ICM connector.
Next using the ohmemter measure the resistance for Zero ohms from the White wire on the Black Coil Connector to the White wire Terminal D on the ICM Connector.
Both of these should be Zero if not then there is a faulty wire.

kimmer

Ok, checked the resistance on both and got 0.L, over the limit. Can I bypass the black connector to see if it starts or is there a diode in it to protect the coil.

FrankieD

if you measured 0L that means both wires are open. Hard to believe that both wires would break unless there is a common issue with either the Black Coil Connector entirely bad or the ICM connector entirely bad. Make sure there is no corrosion on either of the Connectors and while you are measuring the wires try wiggling either end of the connectors to see if you can get a Zero reading.
Pins A & D need to see the 12v from the Primary Coil in order to work.

kimmer

I did bypass the black connector to rule it out and still no voltage. I,v got a bad back problem and this thing has done me in. I'll have it bedded to a place that specializes in corvettes not too far from me. I thank you very much FrankieD for your time and knowledge. If you'r ever in the Bay Area give me a holler and we will take you out for a good dinner. Thank's again, Kim.

FrankieD

Sorry to hear about your back, I know what you mean. I got my share of back problems myself and it doesn't make for fun having to bend over our low vettes. You have been a great assistant in following my directions in trying to isolate this issue, and I think we narrowed it down.
Tell the shop to concentrate their efforts from the Black Coil Connector towards to ICM Connector, I'm pretty sure it's either the Black Coil Connector terminals not making a proper contact to the Coil Primary either because of some sort of corrosion or a wire break.
Thanks for the generous offer of Dinner but we are on this Forum because we have a passion for our Vettes and an enjoyment of helping each other out. Keep us posted and good luck.

kimmer

Hey FrankieD it's running, Just got off the phone to Abel Chevrolet and It seems the 2 new ICM's I put in were both junk. I learned my lesson, no more parts from auto zone or any other cheap chain store. Glad I didn't get my water pump from them. It's funny that the tests did not indicate this, oh well.

93Rubie

You cannot get decent parts from chain stores anymore. All junk. I'm sick of it. I get a lot of stuff from RockAuto.com. Or search the web for NOS. Yeah buddy on NOS, I've hit gold more than once.

FrankieD

hey Kim, congrats on getting this resolved. Glad to hear you're back on the road to enjoy it.. We were very close in our troubleshooting..who would have thought that 2 ICM's were factory defects. Chalk this one up to a great learning lesson.