I just put a new Electronic Control Unit (ECU) in my '86 Corvette. My key seems to be giving the right code, as I get fuel to the rail and spark to the plugs, however, I don't get injector pulse, so no gas is going to the cylinders. I have new injectors. I am told that I need the ECU to read the key chip, to get injector pulse.

How would I go about reprogramming an old chipped key to a new ECU?

  • 1
    If the key is the type where you have the small black object at the base of the key shank, with metal sticking out either side, I believe this is the original "Passkey" design, which you won't get reprogrammed. It's basically a resistor which corresponds to what's in the body control module. If the resistor doesn't match the assigned value in the BCM, there's issues starting the car. Something like this image. Jul 5, 2016 at 17:28
  • thanks .im just trying process of elim.i get no inj.pulse.i get pwr. to inj.but no pulse ? Jul 8, 2016 at 14:17

2 Answers 2


Try this,

1) Turn the key to the Run position and leave it for 10 minutes.

2) Shut the ignition off for 10 seconds.

Repeat steps one and two, two more times and try cranking. If that doesn't work you need to go to a dealer to have the ECM reprogrammed or disable the VATs system.

  • So a total of how many times through the two steps?
    – Cullub
    Jul 7, 2016 at 17:29
  • 1
    @cullub Three times, for a total of thirty seconds key off and thirty minutes key on.
    – Ben
    Jul 7, 2016 at 18:37
  • This does absolutely nothing on VAT models.
    – narkeleptk
    Nov 6, 2019 at 3:11

There is only the option to program out the VATS system in the ECM calpack. The VATS module is where the codes must match ... or rather the resistance of the keys resistor pellet. There are 15 "codes" that correspond to the following resistances (in Kohm).:

1 = 0.402

2 = 0.523

3 = 0.681

4 = 0.887

5 = 1.130

6 = 1.470

7 = 1.870

8 = 2.370

9 = 3.010

10 = 3.740

11 = 4.750

12 = 6.040

13 = 7.500

14 = 9.530

15 = 11.800

You can measure yourself the key resistance to determine which code you have, if you need a new key. Measure in 20Kohm range across the pellet from one side to the other. It's possible you have grime on you key pellet and sometimes cleaning it with alcohol will fix your problem. VATS bypass units are available for ~$50 but they need to know what the key code it has.

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