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VATS is designed to assume that if it discovers a problem with the key resistance while the car is running then it will assume there is a hardware fault rather than a theft and not prevent the car from starting. However, there have been reports of the system "discovering" the fault anew after a reset action such as a battery replacement and then preventing the car from starting. This does not happen consistently so I can't tell you whether it has to do with the amount of time the power is disconnected or some other factor. Obviously you will have replaced your battery within the last 12 years so it's not just replacing the battery which can cause this "reset". I mention it just so you will be cautious about the possibility should you have a need to leave the power disconnected for an extended period.
Good info - thanks! I think I've replaced the battery a couple of times since the Security light came on, but it's always been immediate - sense the battery is getting weak, check it and replace it. However, the day may come when this car is retired from DD duty and parked outside covered for seasonal use. My thought in that scenario was to pull the battery and put it on a trickle charger and re-install it. But that might precipitate the "reset" and ensuing VATS problem you describe. Thanks again!
as many have said before us... ohm your key, get a reistor in that range, cut out the white wires or get one thats made with a plug end on it and unplug them, wire/solder/tape/cover/heatshrink the resitor inplace, test it, if it starts and the security light goes away, you're good to go and button it back up...
I'm a believer in the bypass even if its tuned out. happened to me after i did an entire turbo build and ran, then after doing some new fan harness car wouldn't start. just do it... dont fight it. Bypass the VATS lol
I am reading this thread for the first time. New to LS vehicles. My fun vehicles are all pre OBDii and CAN. I have a 2002 Chevy. I am on my second BCM in the short time that I have owned it(about a year). The first time it blew, I have no idea how it happened. Security light cam on, it threw a 1626 code. I sent it to New York for a rebuild. This morning on my way home from work, I stopped for gas. I left the lights on when I shut off the engine, it dinged a few times when I realized. I filled up, then tried to start the vehicle. On comes the security light, and up pops the 1626 code. Also a 1000 code. I don't remember that from the first incident. Would there be any reason that the headlights would affect the BCM, more importantly the VATS? Would this bypass work to solve this problem? It is kind of expensive to send out the module and get it rebuilt, especially if it happens every time I forget to turn off the lights. Thanks in advance.
Wow, you seem to have the worst luck of anyone on here. Most everyone goes a lifetime without ever having to replace a BCM - let alone two of them. With the exception of the easily fixed cold solder joint problem, BCMs are built to last basically forever... a few do fail but the failure rate is extremely low and many get replaced without actually needing it. The BCM has nothing to do with the headlights so you can rule that out. In fact, the only connection between the BCM and any exterior lights is via the theft deterrent relay which is what flashes the parking lights for the keyless entry confirmation and the optional content theft alarm.
In this case, I suspect that the BCM was never the problem and that your VATS issue is from a worn ignition key, grimy or worn contacts inside the ignition cylinder, or loose or damaged wiring between the ignition cylinder and the BCM. A VATS bypass will certainly eliminate all of those conditions (except the very unlikely case of the wiring being damaged deep in the harness) but you might want to try a couple of other things first... try a different ignition key if you have a spare, clean the contacts on the key pellet using a pencil eraser followed by rubbing alcohol, and clean the contacts inside the ignition cylinder using spray electrical contact cleaner and a pipe cleaner. Often times those things will resolve intermittent VATS issues.
I don't see anything in this thread that helps me but my situation is odd I reckon>>>>
I'm looking to put a 01 5.3L LS motor in my 92 C2500 Flatbed, I found a complete 01 Tahoe thats been wrecked, the guy says it ran when parked but he's used the BCM & driveshaft on a Suburban and after removing the BCM it will no longer run. I'm leary of buying something without hearing it run, so I seen this thread and thought it would have my answer as to how to bypass this BCM so I could fire this Tahoe up to be sure I wouldn't be buying a PIG.
Simple YES or NO is what I'm looking for and if YES some details please
Last edited by 92Flatbed; 03-31-2021 at 11:05 AM.
Reason: More info
The 01 Tahoe used the PassLock system rather than the PassKey system in 4th generation f-bodies. The PassLock system does not rely on a resistor pellet in the ignition key but rather a sensor in the steering column that generates a specific voltage code when the ignition key turns smoothly (i.e. the correct key is being used). The BCM compares that code to its stored code... if they are the same then a fuel enable signal is sent to the PCM allowing the engine to start.
You can program PCM to ignore the lack of a fuel enable signal from BCM to allow the engine to start but that's a lot just to test if it runs.
The 01 Tahoe used the PassLock system rather than the PassKey system in 4th generation f-bodies. The PassLock system does not rely on a resistor pellet in the ignition key but rather a sensor in the steering column that generates a specific voltage code when the ignition key turns smoothly (i.e. the correct key is being used). The BCM compares that code to its stored code... if they are the same then a fuel enable signal is sent to the PCM allowing the engine to start.
You can program PCM to ignore the lack of a fuel enable signal from BCM to allow the engine to start but that's a lot just to test if it runs.
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Ok thanks for the quik response! I'm gonna have to pass on it then even tho the price is excellent but if I bought it & installed it just to find out the motors bad I've invested upwards of $4k for a bad motor. BUMMER!
06-18-2020, 11:55 PM
Flashing an old thread 
