Ok, so here's the deal. My parents just bought a 93 corvette. Not two days after they got it...my mom LOST the keys. (I know). Anyway, they took the vin number, worked off that, which brought up a #15, had a new key made, but it is not starting the car. I tested the new key and it does show as 11,800ohms. But, not being sure if the key/vat was ever replaced before, I went and did the research, and decided to do the resistor bypass trick, but can't get any value to start the car. One thing I am confused by, is if I measure the 2 white wires that are covered in the orange sheath, on that side, I get the correct resistance value the key is set to. However, on the purple and white side of the harness, all I get is 0.00ohms, which I am guessing anybody reading will know the wire I mean, but I will include a picture. So I am wondering if that is right, because it doesn't seem right. If it's going to show continuity 0.00ohms, no matter what resistor I put in there. Does anyone know what would cause that if it's not correct? Or could someone do an ohms test on their's for me? If it is something "else" disabling the car to start, and preventing the vats from reading the resistance at all, what could that be? It seems weird that it would be something else, since it started and ran fine in the short time they were able to.

Also, could someone clarify the wait time in between attempts? Because I have been told 3-4 minutes, which we went with 4 minutes between each test, but I was also told by a local alarm shop the only way to do it is 1 resistor test per hour and if you do more than that and fails, he said it triggers a 'long tamper mode' in which you are locked out for 24 hours...which I haven't read anywhere. Thanks for any help. Desperate to get this figured out...it's a 6 speed and I haven't even gotten to test drive it, yet!

 

You might see if a local lock shop has a VATS Interrogator or if you have a 'relationship' with a GM dealer ask them. If you have the assortment do as IHBD mentions BUT if you don't and wanted to a DIY - in the past users have used a 10K potentiometer and it will do all except #15 I believe. I have a friend who used to start in the middle with 7, then go +1 and next -1. 7, 8, 6, 9, 5, 10, 4, 11, 3, 12, 2, 13, 14 & 15. He insisted that he got there quicker 90% of the time. For '93 you can toss #1 as it wouldn't have been done factory with 1. It would have to have been done intentionally with a programming.

Where are you located? Some have Interrogators. I do.

 

The security light is on solid with the key in run every time, on every resistor. Which is what I went by the most to judge whether or not the resistance was right or not. But as I said, I was doing them in 4 minute intervals. Though I started at the 15 end, so 15, 14, and 13 might can be ruled out, if you get a 3 chance grace limit before it kicks it to 12 minute intervals. And, I was actually using a '10k' potentiometer for all but 14, and 15, because it would only do up to about 9800 or so. The VATS Interrogator really doesn't look much different than what the resistors are doing, other than maybe more convenient. But I'm willing to try anything. I'm near middle TN (Nashville). I just want to make sure to rule out anything else that might be causing it. Theft deterring relay stuck? Or maybe a failed relearn procedure, which we attempted first, but the security light never went off there either. But I guess to even enable the relearn procedure, the resistance for the key has to be right. Now, in using the potentiometer, I was getting as close to the ohms number on the chart as possible, but could rarely get it dead accurate...but from looking at the charts on the internet, it has a minimum and maximum allowable tolerance, which it was always well within that range.

 

Do you have the FSM for your '93? In your original post you mentioned coming up with a #15 from somewhere - WHERE? GM dealers haven't been able to retrieve VATS codes for many years. You also mentioned attempting a 'RELEARN' - what did you do in that attempt? Unless a CCM is cleared of all information it can't be relearned.

If you have the FSM the 8D section covers the use of the DIC to check various aspects of the complete ECM/CCM diagnostics. You could maybe check for the A/D Counts that the CCM is thinking it sees

 

I don't have a service manual. My understanding was they cut a new key using the #15, based on the vin number, and I thought I heard my dad say he got it from the dealer. I can double check that tomorrow. On the 'relearn' I unhooked the battery, turned on the ignition, waited 10 minutes, and the security light would never go out. We also tried with the 3x 30 minute method, which it never went out on that either.

 

Right, I kinda ruled out the relearn early on, but when nothing works, you start to question everything. I was using a digital voltmeter to measure the potentiometer everytime and adjust it. I am planning to go back over there tomorrow and will try the procedure in 15 minute intervals instead of 4 minute ones, and I will start with the middle #7 and work my way out from there. I just want to be armed with as much information as I can, since it didn't work today, but I think I already had everything worked out, except for the 15 minute interval between tests.

 

Ok, so today I waited the 15 minutes, and it ended up working. Looks like it is 2370ohms #8. I was using a pot so I don't want to leave that in there so I am going to find a resistor off a scrap board to equal that value or put some together in series if I need to. Anyway thanks for all the help.