Ignition key ohm measurement
Bear in mind that the key you get with the used module will almost certainly not work with your ignition. You'll have to measure the resistance on the pellet and then get a new key cut that matches the cuts of your original but has the resistance value of the new module. That may not be cheap - I've heard of dealers charging $80 or more for a new key.
Are you saying that, besides the different VATS values, every key of those 15 has its peculiar cut?
Yes, of course the keys have different cuts just like keys that don't have a resistor in them. The cuts on the key are what engage the tumblers in the ignition cylinder and allow it to physically turn to the run and start positions. The resistor is just an added electrical safeguard that prevents the car from starting if a thief broke or removed the ignition cylinder (usually with a slide hammer) so they could turn it with just a screwdriver. So what you need is to get a new key cut to match your existing key (so that it will turn the lock) but using a key blank that has the built-in resistor that matches the resistance of the key you get with the new module.
Yes, of course the keys have different cuts just like keys that don't have a resistor in them. The cuts on the key are what engage the tumblers in the ignition cylinder and allow it to physically turn to the run and start positions. The resistor is just an added electrical safeguard that prevents the car from starting if a thief broke or removed the ignition cylinder (usually with a slide hammer) so they could turn it with just a screwdriver. So what you need is to get a new key cut to match your existing key (so that it will turn the lock) but using a key blank that has the built-in resistor that matches the resistance of the key you get with the new module.
Without the original key to measure for the pellet resistance, your other option is to try all the possible values until you find the correct one. Fortunately, there are only 15 different values so it's not an impossible task. In fact, you can buy VATS boxes that have all possible combinations built-in and controlled by a set of DIP switches - just plug it into the VATS wires under the steering column and try each value in turn by changing the DIP switches. One I'm familiar with is made by DEI (the makers of Viper alarm systems), part number 20402. I think DEI has discontinued it but it's still available online in places like ebay for about $30. Another is the Gator VATS Bypass Module (their part number VBM054). It is available online for about $36 from the manufacturer, Gator Tools. Either one will have you up and running in about 10 minutes.
You could do it yourself by buying all the resistors needed to create each of the 15 values (resistors are dirt cheap) and then trying each combination until you find the one that works. This is the least expensive option but a lot more work and a lot more time scrunched under the steering column.
Here is a chart of all the values and what resistors are necessary (note that almost all require combinations of two resistors to make the correct value):
The VATS number and corresponding resistance is shown in the shaded areas. Below each is the combination of standard resistors needed to make the value and the percentage that the resulting value is off from the expected value. All of the combinations listed are well within the tolerance allowed by VATS. Combinations with a + are wired in series (end to end) while combinations with || are wired in parallel (side by side with ends connected together).
Last edited by WhiteBird00; Dec 26, 2023 at 10:13 AM.
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So now the speedo is acting like the tach and the tach doesn't move at all. i am thoroughly confused now. Any ideas?
I’m having a similar problem.
Thanks







