What computer box does the odometer read from?
Thread Starter
Instructor
Joined: Jul 2006
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From: Erie PA
What computer box does the odometer read from?
I have a 93 with 24,000 miles that I bough last year. When I went to my Chevy dealer to purchase a 2nd set of keys with a VATS chip the guy at the parts counter ran my VIN number into the computer, my car called for code #15 key pellet. I got home and the key would turn but not start the car. Long story short: at some point the previous owner changed the computer and now it takes a code #6. My question, would changing the computer that controls VATS have an effect on my odometer. The car is in very good shape but I wonder if it may have higher mileage
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Joined: Dec 1999
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The CCM holds the odometer reading and the VATS code. The CCM also has the VIN programmed into it so a service tech with a Tech-1 scanner can read the VIN that is in the CCM. If the VIN appears different, the CCM is from another car.
If a different CCM was installed in the car, the odometer value would be from that car. If a new CCM was installed, it would have to be programmed with the then-current mileage, the correct VIN and the VATS code. But the mileage has to be entered within 100 miles of the install of a new CCM or it will lock out any attempts to program it.
Another possibility is that the parts guy mis-keyed your VIN into his terminal. He may have gotten an incorrect VATS key value based on some other VIN, cut the key and when you tried to start the car, the PASS-Key system saw the incorrect value and disabled the cranking and fuel delivery system.
When this happens, a 3 minute timer starts. If you try to use the key again before the 3 minutes passes, it simply resets the timer. Even disconnecting the battery will not reset the timer. The CCM stores the state of the PASS-Key system in EPROM and simply sees it again when power is restored. Even trying to use your "good" key within the 3-minute period will not start the car. You have to wait.
The dealer (or a good locksnith shop) should be able to simply read the key pellet by using a Ohm meter. The resistance value of the pellet corresponds to a table of the 15 possible key pellet resistance values. Then they select the right key by value and cut it to fit.
If a different CCM was installed in the car, the odometer value would be from that car. If a new CCM was installed, it would have to be programmed with the then-current mileage, the correct VIN and the VATS code. But the mileage has to be entered within 100 miles of the install of a new CCM or it will lock out any attempts to program it.
Another possibility is that the parts guy mis-keyed your VIN into his terminal. He may have gotten an incorrect VATS key value based on some other VIN, cut the key and when you tried to start the car, the PASS-Key system saw the incorrect value and disabled the cranking and fuel delivery system.
When this happens, a 3 minute timer starts. If you try to use the key again before the 3 minutes passes, it simply resets the timer. Even disconnecting the battery will not reset the timer. The CCM stores the state of the PASS-Key system in EPROM and simply sees it again when power is restored. Even trying to use your "good" key within the 3-minute period will not start the car. You have to wait.
The dealer (or a good locksnith shop) should be able to simply read the key pellet by using a Ohm meter. The resistance value of the pellet corresponds to a table of the 15 possible key pellet resistance values. Then they select the right key by value and cut it to fit.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 153
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From: Erie PA
a used CCM installed.
Thanks for the info; I had a mechanic run a interrogator on the computer that’s how I found out that it took a different VATS code. The CCM was changed (was from a different car). This explains the low mileage. Thanks again for your help.
