1997 3500 vortec issue

[Steve A]

Well it was the same thing with the old ignition and wiring the only difference is that the security light was on with the old stuff and it is off now

Does it have an aftermarket security system, if so uninstall it. Or is it the security light in the instrument cluster, if that's the problem it may be VATS is preventing it from running. Right in that time frame GM started using keys with a RFID chip, which means a switch with key replacement along with a wiring harness change won't fix it. The key has to be programmed to the PCM.

 

[HotWheelsBurban]

What the passlock VATS ( vehicle anti theft system) does is this: the passlock module under the dash gets a signal from the ignition switch in the column when the vehicle is put into start position. If these signals don't agree, another signal is sent to the PCM and it shuts off the power to the fuel pump relay. This takes a second or two, and when the relay loses power, it shuts the fuel pump off. I had this happen on my 99 Burb in 2019. The only real "fix/cure" was to have the passlock/VATS system deactivated in the PCM. A tuner can do this for you, but it'll probably cost a couple hundred bucks or more. $250 in my case, but it cured what all the relearn procedures and internet tricks wouldn't.
I think there's some difference between the 96-97 version and the 98-99 version though; more experienced people than me can chime in here.....
Good luck, hope this helps.

 

[df2x4]

Right in that time frame GM started using keys with a RFID chip, which means a switch with key replacement along with a wiring harness change won't fix it. The key has to be programmed to the PCM.

FWIU, it's a resistor in the ignition cylinder which sends signal to the Passlock module. There's no chip in the actual key.

I think there's some difference between the 96-97 version and the 98-99 version though; more experienced people than me can chime in here.....

As far as I know Passlock should be in '98+ trucks only. Neither of my '97s have it.

 

[HotWheelsBurban]

The key does not have a chip in it. Neither do the keys to our 06 Denali. GM apparently didn't go to the chip keys on the trucks till the 07s....but they used them on some cars in the mid- late 80s; Camaro and Corvette primarily.
On the other hand, this 2001 ferd has a chip key. $80 to replace, and that's the cheapest guy that comes to your location. Ford store wants $125 at least, and you have to bring them the truck. If we could still drive it I wouldn't be trying to sell it( and the keys we had for it wouldn't have been misplaced.....)

 

[Rusty c]

update i ordered a new ecm pcm programmed without the security and have that solved but i still have some wiring issues between the 96 cab harness and the 98 engine harness no tac or gauges but still working on it