Corvette LT1 No Spark

New member here. I have an 94 C4 with under 50k miles. The car ran fine when I put it away for winter storage, but now it wont start. No spark.

I read alot on the forums and watched some of the videos on youtube. I followed the test I found on line and if I did this correctly, my B terminal (White IGN control) for the ICM harness doesn’t do anything when I crank the motor over… i read to switch your meter to ac scale and it should read 1 - 4 vac? Well, iIget nothing… I have 12v at A and D on the ICM. For the opti I have 4.99V at A and B, I have 12V on C, but it’s that B terminal on the ICM harness… So, what does this mean? Is my computer bad? Or Opti?


By any chance is the SECURITY light illuminated in the dash while cranking?

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Optispark systems are notorious for not being optimum. I don;t have a trouble tree in front of me for this car so… if you do, pay attention to it. If you don’t, you might be better to ask this one a Corvette forum.

I thought It was. I’ll make sure tonight after work. If it wasn’t then what should I look for?

I was thinking the optispark, but find it odd it would fail from sitting during winter storage, but i guess its possible moisture got in there and corroded everything while sitting? I just want to make sure its the opti before I go through the hassle of changing it at my storage unit.

I tried the C4 corvette forums and so far no answer.

In '94, I believe the systems was still known as VATS or Passkey1/2. They were the most simple security systems relying on a chip resistor in the key. That resistor connects via the ignition cylinder to the VATS module that reads the key and enables the ignition if the right value is read. If not, the security lamp is illuminated and the system goes into lock mode for around 10 minutes.

The common failure mode is when the little wires in the lock cylinder break from repeated stress of rotation when the key is turned.

If this is the type of system you have, it is the easiest to defeat. A simple resistor matching the key value can be inserted into the cable connector coming down the column.

See this link for some information-

That is exactly how they fail. Not the best design!