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I think it's important to clarify that the starter cranking does not rule out a VATS issue.
Your comments made me go back and read through books one and two.:)

In the pass key section the trouble shooting chart #2 is titled: "Engine Cranks But Won't Start"
In the DTC 46 it says starts and stalls in 1.7 seconds. But there is no test chart for "Starts But Stalls in 1.7 seconds"

What I got out of it all is that a VATS module does not always trigger the theft deterrent relay and that can be normal operation. If the PWM does not make it to the PCM it may sound like the engine started (1.7sec).

More importantly is does not seem possible to easily diagnose a VATS problem with out a code reader and a multi meter that will respond in some way to the PWM.
A cheap digital meter might just read blank or "OL" or change ranges where a analog or better digital meter would show voltage(and/or hertz). As usual a oscilloscope would be handy.

This may be a long shot,but look closely at the grounds bolted to the icm/ignition coil mounting stud at front driver cyl head.The VATS grounds there.These eyelet grounds are notorious for corroding and or breaking off the eyelet lug,if never attended to.
Jim
Other than the key resistor input all the VATS circuits ground other components. So a bad ground might allow the VATS to seem to function but not have enough conductivity to ground the relay or send the correct PWM to the PCM.

On old cars I add ground cables. In this case I add one to the ICM bolt to the battery ground wire.(at the fender lead or block lead)

It is amazing how much better the charging system on some cars operate when you add a ground wire from the alternator case to a negative battery lead wire. Factory alternator to block electrical connections are not always perfect after 25 years.
 

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Your comments made me go back and read through books one and two.:)

In the pass key section the trouble shooting chart #2 is titled: "Engine Cranks But Won't Start"
In the DTC 46 it says starts and stalls in 1.7 seconds. But there is no test chart for "Starts But Stalls in 1.7 seconds"

What I got out of it all is that a VATS module does not always trigger the theft deterrent relay and that can be normal operation. If the PWM does not make it to the PCM it may sound like the engine started (1.7sec).

More importantly is does not seem possible to easily diagnose a VATS problem with out a code reader and a multi meter that will respond in some way to the PWM.
A cheap digital meter might just read blank or "OL" or change ranges where a analog or better digital meter would show voltage(and/or hertz). As usual a oscilloscope would be handy.


Other than the key resistor input all the VATS circuits ground other components. So a bad ground might allow the VATS to seem to function but not have enough conductivity to ground the relay or send the correct PWM to the PCM.

On old cars I add ground cables. In this case I add one to the ICM bolt to the battery ground wire.(at the fender lead or block lead)

It is amazing how much better the charging system on some cars operate when you add a ground wire from the alternator case to a negative battery lead wire. Factory alternator to block electrical connections are not always perfect after 25 years.
I agree Z09B4U,
The importance of quality grounds cannot be understated.Good post.
Jim
 

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Stopped by to read. I have a similar issue, but mine seems more obvious. SOME times when I go to start the car, it does nothing, and the passkey light comes on, and I'm screwed for 3 mins. After 3 mins, car will start fine and drive fine. Amazing how long 3 mins is when you are sitting in a black car in Florida without AC.

Seems to happen randomly with both keys, so I guess first step is to change module?
 

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I guess first step is to change module?
The next step would be to check the ignition lock cylinder to VATS wiring. If you do not like trouble shooting things get expensive.
Some locksmiths will know how to clean the pellet contacts without washing out the ignition cylinder's lubrication.
If you shop around a new "re keyed" lock cylinder may not be expensive. It is mechanical and will wear out at some point and not make good contact with the key's "resistance pellet"cleaned or not.

Changing the module will change the VATS resistance. So first you do the random resistor test until you find the correct value for the "new" VATS then you have to replace your keys with ones that have the correct "resistance pellet" for the "new VATS"

PASS KEY II Information (AKA VATS)
 

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The next step would be to check the ignition lock cylinder to VATS wiring. If you do not like trouble shooting things get expensive.
Some locksmiths will know how to clean the pellet contacts without washing out the ignition cylinder's lubrication.
If you shop around a new "re keyed" lock cylinder may not be expensive. It is mechanical and will wear out at some point and not make good contact with the key's "resistance pellet"cleaned or not.

Changing the module will change the VATS resistance. So first you do the random resistor test until you find the correct value for the "new" VATS then you have to replace your keys with ones that have the correct "resistance pellet" for the "new VATS"

PASS KEY II Information (AKA VATS)
The problem that I've had is that its totally random when it happens. It might be good for 2 weeks, but then happen 3 days in a row. All 3 keys I have seem to have the problem and they are all 68.x k ohms. I guess changing out the lock cyl, other than changing the key doesnt have any other impact? I'd just have to cut a new key with the same resistor
 
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