How does VATS prevent the car from starting? - Chevy Impala SS Forum
 
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post #1 of 5 (permalink) Old 11-12-2012, 09:29 PM Thread Starter
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How does VATS prevent the car from starting?

Like the title asks, how EXACTLY does the vehicle anti-theft system actually preveent the car from starting? Does it allow the starter to turn the engine over but prevent spark ignition or does it actually prevent the starter from engaging?

Background

Once or twice a year, my wife's B4U Caprice will absolutely refuse to engage the starter. Interior lights, radio, headlights, flashers, and everything on the dash works fine but when you turn the key forward you don't even get so much as a click out of the starter. We replaced the starter, added Gary's cables, and got new keys cut last year before it started working but it seemed like it just started working again on it's own rather than because of anything that we did. This year though, the "VATS" dash light comes on and stays on even though it's been programmed out for years. I'm trying to figure out where to go from here........

Thanks,
Jim

1968 Camaro -my first car.
1995 Purple Pearl B4U Caprice
1995 Black/White 9C1 Caprice--NADACOP
1995 Purple Pearl L99 Caprice
2012 Alto Gray Metallic 9C1 Caprice--The HoDag-Solo axle back exhaust, improved racing OTR CAI intake.
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post #2 of 5 (permalink) Old 11-13-2012, 06:19 AM
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Maybe these might help...

http://tpiparts.net/vehicle_anti_theft_system__vats_/

http://vats.likeabigdog.com/

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post #3 of 5 (permalink) Old 11-13-2012, 08:08 AM Thread Starter
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Thank you for the response.

The second link seems like it will be very helpful. Both links though are somewhat ambiguous as to exactly how the VATS system prevents the car from starting. Both seem to agree though about a signal being sent to the PCM from the ignition switch that energizes a starter relay that should prevent the engine from even cranking over. This is the part that I'm trying to diagnose now. A friend suggested hooking a volt-meter into the circuit at the starter wire and checking the reading as I try to crank the car to see if the circuit is energized.

The links differ on whether it's the fuel pump or the injectors though that would prevent ignition once the engine starts turning over. In one case the PCM is telling the injectors to stay closed but allowing the fuel pump to pressurize the system which would have the same net effect as not allowing the fuel pump to run at all to pressurize the system. From a diagnostic point of view however the difference is huge.

In my case, when I turn the key the starter doesn't even try to engage. The VATS idiot light comes on and stays on and the fuel pump primes. I'm just trying to figure out where to go from there but I at least have something else to try thanks to the links you've provided.

Thanks,
Jim

1968 Camaro -my first car.
1995 Purple Pearl B4U Caprice
1995 Black/White 9C1 Caprice--NADACOP
1995 Purple Pearl L99 Caprice
2012 Alto Gray Metallic 9C1 Caprice--The HoDag-Solo axle back exhaust, improved racing OTR CAI intake.
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post #4 of 5 (permalink) Old 11-13-2012, 09:46 PM
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I've done a 94 RMW and 96 Camaro the same way.

1. Measure the resistance on the key.
2. go to Radio Shack and buy resistors in the proper range.
3. cut them in at base of steering column.
4. No programming necessary.

Cost about a dollar for resistors.

There are some photos, threads around on this. The pics were on the shobox site..... forget the link exactly. PM me if you want details on how to do it, but a search on here should reveal.

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post #5 of 5 (permalink) Old 11-18-2012, 06:51 PM Thread Starter
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It actually ended up costing around $10 for the five resistors and heatshrink tubing and electrical connectors.
I built the bypass after the car had to be towed home for another no-start situation. I thought the car was OK since it started every time all last week when I was driving it. The flatbed driver said that he had run into this several times and said that you needed to turn the key forward for ten minutes or so to reset the pass-key fault.
When I first installed the pass-key bypass the car still wouldn't start but has started every try so far after letting it sit for fifteen minutes with the key turned forward to reset the pass-key fault. So far so good.

This link has a better explanation of how VATS works but still doesn't seem to match my situation....... http://home.hiwaay.net/~davida1/passkey.htm

Jim

1968 Camaro -my first car.
1995 Purple Pearl B4U Caprice
1995 Black/White 9C1 Caprice--NADACOP
1995 Purple Pearl L99 Caprice
2012 Alto Gray Metallic 9C1 Caprice--The HoDag-Solo axle back exhaust, improved racing OTR CAI intake.
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