1991 C4 - Immobilizer?

[Tomas Portugal]

Hello.
I've a '91 corvette zr1 but it don't start the engine. When i turn on the key, nothing happens. The light "anti-theft" is on.
The electrician says that the problem it's the immobilizer. How I can solve the problem?
Need a control unit for ignition??? I can´t find it or repair nowhere.

I heard about a immobilizer "bypass"... could be the solution??
I need to re-code the keys??
I live in Europe (Portugal). Sorry about my english.
Please help me.

Thank's a lot.
Tomas.

[1990-C4-41001]

Hello Tomas.

I will try to help you.

First, purchase some electrical contact cleaner. After car has sat for 30 minutes without you trying to start it, spray the ignition lock (the opening where you put the key) with some cleaner. Only spray for 1 second, directly into the place where you put the key to make the car start.

Put the key into the ignition lock and remove it 3-4 times. This is to clean off the contacts within the ignition lock.

Put the key back in and turn the key to the run position but do not try to start the car.

Look on the left of the instrument panel and see if the security lamp is lighted. If it is, the car is not going to start and you have more problems then just the key.

If the light is not on, you should be able to start the car now.

This test will also mean that the contacts within the ignition lock are worn and you either have to repair that problem (difficult and expensive) or you can bypass the VATS system.

If you decide to bypass the VATS (Vehicle Anti-Theft System), first you must measure the resistance of the small pellet that is in the key itself.

If you cannot do this yourself, have the electrician measure it with a digital ohmmeter and write down the value.

Compare the resistance value you measured to the following chart. It has the code number you need to purchase a bypass system. (The measured value will probably not exactly match the resistance value below. If that is the case, find the value from the list that is closest to what you measured and use the code associated with it.)

Ohms Code
402 1
523 2
681 3
887 4
1130 5
1470 6
1870 7
2370 8
3010 9
3740 10
4750 11
6040 12
7500 13
9530 14
11800 15

Once you have the code, call Eckler's Corvette Parts in Florida, USA at 01-321-269-9651. They have people who speak many languages other than English if you do not speak English well. Once you are talking to a sales person, tell them you wish purchase a Security Override System, item A9133 and also give them the code number you determined from the chart above. The cost should be about $30.00 USD plus shipping. There will be instructions for installation furnished with the bypass kit. Once you've installed the part, the car should always start. Your alarm system will still work (the alarm that senses if the car door is being opened by a criminal) but the VATS system will no longer function.

I hope this helps you.

John

[c4c5specialist]

HI there,
You can do that, or you can purchase the ignition lock cylinder and 2 keys and have them installed.
If your security light is on, its not seeing the key.
So, you can override if you wish as stated above, or you can replace the lock cylinder.
Either way, I am sure you will be just fine.
Allthebest, c4c5

[Tomas Portugal]

I'll follow your instructions.

Thank's a lot. I'll let you know the results.

Tomas - Portugal