LT1 Security / PCM issues?
LT1 Security / PCM issues? Completely baffled with my 1996 Z28 M6 right now.
When I try to start the car it does nothing and the security light comes on.
Bought a new key. This made no difference.
Tested the voltage going through the key switch(orange wire under dash). Tested within 1% of the value of the key.
Tried the resistor trick. This worked for a while. The resistors had same value as the key chip. I drove the car for 2 weeks like this. Made an exact copy of the resistors and they did not work.
Pulled into the gas station and hit a pot hole pretty hard core. Got gas and the car has not started since.
I then tried the vats override box from ebay. This has three wires, black blue and red. Black is ground, red is 12v accessory and blue goes into pin 25 of the red block on the pcm. This box has a light that lights up, car still does not start. I still have to wait the 3 min with the security light on.
The PCM was wet when I pulled it out, but its metal. Didnt look too bad, but figure its worth mentioning.
What is the issue with my car?
When I try to start the car it does nothing and the security light comes on.
Bought a new key. This made no difference.
Tested the voltage going through the key switch(orange wire under dash). Tested within 1% of the value of the key.
Tried the resistor trick. This worked for a while. The resistors had same value as the key chip. I drove the car for 2 weeks like this. Made an exact copy of the resistors and they did not work.
Pulled into the gas station and hit a pot hole pretty hard core. Got gas and the car has not started since.
I then tried the vats override box from ebay. This has three wires, black blue and red. Black is ground, red is 12v accessory and blue goes into pin 25 of the red block on the pcm. This box has a light that lights up, car still does not start. I still have to wait the 3 min with the security light on.
The PCM was wet when I pulled it out, but its metal. Didnt look too bad, but figure its worth mentioning.
What is the issue with my car?
On The Tree
Joined: Jan 2010
Posts: 133
Likes: 0
they are know for this this is how you can fix it. go to the chevy dealer and buy a new cylinder make sure you have a new key made and the new key fob is programed take off the pannel under the stering colum there will be one wire yellow that runs up the colom to the cylinder, that usuallly has a bad connection. plug in the new cylinder and install key so it will read the pass. this will bypass it and you can use the other key to start the car from the colum . tape the key in the cylinder under the dash and zip tie it up. its hillbily but i did it 3-4 times on other fbodys with pass key.
Doesnt the box that I bought work to bypass the key system?
http://cgi.ebay.com/ebaymotors/GM-VA...Q5fAccessories
Also, how much did a new key switch cost you? They are about 50 on ebay.
Could I take it back it this isnt it?
Also, we tested the resistance of my current key switch and it is reading the value of the key (9.5 ohms)
Thanks
http://cgi.ebay.com/ebaymotors/GM-VA...Q5fAccessories
Also, how much did a new key switch cost you? They are about 50 on ebay.
Could I take it back it this isnt it?
Also, we tested the resistance of my current key switch and it is reading the value of the key (9.5 ohms)
Thanks
On The Tree
Joined: Jan 2010
Posts: 133
Likes: 0
who knows it could be making things worse you most likely gonna need the cylinder replaced or hill billy it like i said i drove mine for 6 years and never had another problem it takes 15 min to rig up just make sure the key has the same resistor. better yet if you have a set of keys just by a cyiinder and give it a try for a few $$
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Teching In
Joined: Mar 2010
Posts: 23
Likes: 1
From: Fort Worth, TX
When the lock is rotated, Ignition voltage is applied to the Body Control Module and pellet resistance is read at this time. The Pellet resistance is read across connector C3 terminals "C2" and "D7" which is then compared against the resistance value stored in the module. If the Key Resistance Pellet is the proper resistance, connector C3 terminal "C11" is grounded, energizing the Theft Deterrent Relay. At the same time, a signal is applied at connector C3 terminal "D8" to enable the Powertrain Control Module (PCM). When this signal is received by the PCM, it allows fuel injector pulses to begin. If the Key Resistor Pellet is the wrong value, the Body Control Module will shut down for 3 minutes + or - 18 seconds. During this interval, there will he no output at connector C terminals "C11" or "D8" and the SECURITY" Indicator will illuminate. The Ignition Switch input is ignored during this shut down period. For this reason, the timer will run and the "SECURITY" Indicator will rein am illuminated with Ignition on or off. Once the timer has completed its 3 minute + or - 18 second shut down, the next time Ignition is cycled from off to on, the Body Control Module timer is reset. A key having the correct code can then be used to start the Engine.
I have also heard that if the 'key in ignition' sensor in the key cylinder isn't working properly then that could cause problems, but I have personally not run across this.
I have also heard that if the 'key in ignition' sensor in the key cylinder isn't working properly then that could cause problems, but I have personally not run across this.
On the right side of the dash, there is a gray relay that has the purple wire going to it. If you pull the glove box, it's buried in there. I unplugged the relay and used a hard wire to jump the terminals (effectively disabling the relay and making it a solid wire all the way through. That takes out all the security I think and let's you start the car. worked for me. I drove it that way for a couple of weeks before programming it out.
TECH Veteran
Joined: Dec 2008
Posts: 4,145
Likes: 61
From: Little Rock, AR
On the right side of the dash, there is a gray relay that has the purple wire going to it. If you pull the glove box, it's buried in there. I unplugged the relay and used a hard wire to jump the terminals (effectively disabling the relay and making it a solid wire all the way through. That takes out all the security I think and let's you start the car. worked for me. I drove it that way for a couple of weeks before programming it out.
Makes sense, like I was saying, worked for me the way I did it. I didn't know what else was involved in the VATS setup either so I eliminated what I could. If he jumps this connector and it doesn't start, then he should at least know that it is VATS and not something else (assuming he's got spark, fuel, and the starter is fine and no wiring issues)
