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Hey guys, long time lurker looking for some insight on my 1999 Trans Am. I've been having an issue for the last 3 months where the security light will come on and the check engine light comes on and the car refuses to turn over. I measured both keys I have at 20k at 1.47 ohms, so I taped 2 resistors together and they come out perfectly at 1.47 ohms. But no matter how I put them into the purple and white connector, the security light stays on. The security light has come on and off since I first bought the car but it typically starts after a few tries. Also the radio and windows would randomly kick out, but always come back if you restart the car. Could it be a bad ignition switch? Would the car still fail the VATS verification if the switch is good or bad? Would the BCM going bad be an issue? The car is stuck with the alarm engaged with the battery disconnected because it won't recognize the key. I would use my fob do disable it but it just died a couple months ago.
You will note that there is no 1.47 ohm value in the list. In fact, there is no value lower than 402 ohms but there is a 1470.
I guarantee that if you are using resistors totaling less than 2 ohms, you have the wrong values and that is the source of your VATS problem.
Exactly what resistor values are you using? They must have been labeled when you bought them or you can determine the values from the colored stripes on the resistors themselves.
Hey guys, long time lurker looking for some insight on my 1999 Trans Am. I've been having an issue for the last 3 months where the security light will come on and the check engine light comes on and the car refuses to turn over. I measured both keys I have at 20k at 1.47 ohms, so I taped 2 resistors together and they come out perfectly at 1.47 ohms. But no matter how I put them into the purple and white connector, the security light stays on. The security light has come on and off since I first bought the car but it typically starts after a few tries. Also the radio and windows would randomly kick out, but always come back if you restart the car. Could it be a bad ignition switch? Would the car still fail the VATS verification if the switch is good or bad? Would the BCM going bad be an issue? The car is stuck with the alarm engaged with the battery disconnected because it won't recognize the key. I would use my fob do disable it but it just died a couple months ago.
This is interesting. My 2000 SS security light is always on. Never have a starting problem but my Windows and radio sometimes kick out. Interesting connection!
According to the color code I'm using brown black red gold which says is 1k ohm and the other is yellow violet brown gold which says is 470 ohms. I'm just quoting the reads from the 20k setting on the voltmeter as the 1.44 and 1.46 values. Do you think wiring in a couple of 1ohms would help?
From: Jacksonville, FL (originally from Toronto Canada)
Originally Posted by Mappinsj
This is interesting. My 2000 SS security light is always on. Never have a starting problem but my Windows and radio sometimes kick out. Interesting connection!
Two completely separate issues. The power windows and radio issue is caused by an intermittent failure of the retained accessory power (RAP) circuit in the BCM which in turn is commonly caused by a bad solder joint on the circuit board of the BCM. There is a simple fix here: https://ls1tech.com/forums/general-m...blems-fix.html.
The SECURITY light in the instrument cluster is controlled by VATS. If it detects an invalid resistance value from the ignition key, the light will be solidly lit. If it fails to detect any resistance value, the light will be flashing. If the failure occurs while the engine is already running then the system assumes a fault and will still allow the car to be restarted. Otherwise, the system will disable both the starter relay and the fuel enable signal from the PCM effectively preventing the car from starting.
Since your car continues to start, the system must be considering the wrong resistance as a system fault. However, you must get it fixed before you disconnect the battery for any reason because when you reconnect the battery it will no longer be considered a fault and your car won't start.
From: Jacksonville, FL (originally from Toronto Canada)
Originally Posted by Snowman5677
According to the color code I'm using brown black red gold which says is 1k ohm and the other is yellow violet brown gold which says is 470 ohms. I'm just quoting the reads from the 20k setting on the voltmeter as the 1.44 and 1.46 values. Do you think wiring in a couple of 1ohms would help?
No, you have the correct two resistors to produce the required 1470 ohms. Remember, you want the total resistance to be one of the 15 listed values expected by VATS - you're not trying to match the key.
If you have them connected the way they are shown in the photo (i.e. side by side with the ends connected together) then you have them in parallel rather than in series. Those two resistors in parallel produce a net resistance of only 319.73 ohms which is not valid. You must connect those two resistors in a single line (end to end) to achieve the required 1470 ohms.
I don't understand how they are not in a single line either way. One end goes into one side of the vats connector and the other end of the resistor the other side to complete the circuit. Do the resistors have to be facing a specific way?
From: Jacksonville, FL (originally from Toronto Canada)
In the photo, only one end is visible. If the two loose ends we can't see are connected to one wire and the two connected ends in the black sheathing are joined to the other wire then the resistors are in parallel.
one end not shown goes into one side of the purple and white connector and the other not shown goes into the other side of the purple and white connector. They are only joined on the one side and I'm putting each side of a resistor into a slot. how should i correct this?
Last edited by Snowman5677; Dec 31, 2015 at 01:16 PM.
From: Jacksonville, FL (originally from Toronto Canada)
Unplug the connector and tuck away the end with the two white wires in the orange sheathing so that it is out of the way (it is no longer needed). Then connect one end of your resistor combination to the purple/white wire and the other end to the white/black wire on the other end of that connector. Make sure they make secure, solid contact because any looseness will cause problems. In fact, it's much better to splice directly into the wires themselves than to just plug the loose ends of the resistors into the connector.
I've tried a custom built resistor that I tested at 1470 and then 1460 and neither worked. I'm skiddish to splice it because I should be making solid connection through the back. I put 2 clips inside the front as well with the same resistor and no luck still.
Hey I ended up biting the bullet and cut off the connector. I attached alligator clips to the stripped wires and wired in 2 different resistor combinations. One that should have totaled 1470 ohms but tested at 1430 and one that I added 10 ohm resistors to in order for it to test at 1470 ohms. No matter how I wire it, I still get check engine and security light stays on.
Two completely separate issues. The power windows and radio issue is caused by an intermittent failure of the retained accessory power (RAP) circuit in the BCM which in turn is commonly caused by a bad solder joint on the circuit board of the BCM. There is a simple fix here: https://ls1tech.com/forums/general-m...blems-fix.html.
The SECURITY light in the instrument cluster is controlled by VATS. If it detects an invalid resistance value from the ignition key, the light will be solidly lit. If it fails to detect any resistance value, the light will be flashing. If the failure occurs while the engine is already running then the system assumes a fault and will still allow the car to be restarted. Otherwise, the system will disable both the starter relay and the fuel enable signal from the PCM effectively preventing the car from starting.
Since your car continues to start, the system must be considering the wrong resistance as a system fault. However, you must get it fixed before you disconnect the battery for any reason because when you reconnect the battery it will no longer be considered a fault and your car won't start.
I have unplugged the battery. I have changed the PCM and the vats is never worked I can put any key inside at any ohm
Something else is going on here. Adding a 10 ohm resistor to a 1430 ohm circuit, should not jump you up to 1470 ohms.
Are you holding the tips of your meter leads between your finger tips when you're reading the resistance? You are getting into the range of being able to affect the readings by touching any of the metal conductors.
Do you have it still connected to the wiring in the car? You will want to measure the resistor string that you built by itself, before you wire it in.
Also, reading your resistance straight from the key can get tricky, I've always found it easier to just read the two wires in the orange sleeve, after I've unplugged that connector in your picture.
I've done all of what you said above. I added multiple 10 ohm resistors to bump it up from 1430 to 1470. I tried reading from the orange side and it will give 1460 as the reading. Then I swapped out the alligator clips to the resistor and tested it at 1470 ohms.
Last edited by Snowman5677; Dec 31, 2015 at 07:46 PM.
Things have only continued to go downhill for my car. Tried grounding the starter relay to see if I could get it to crank and now the car is just stuck in alarm activated mode. Before the door alarm was set but now the car just starts honking as soon as you hook up the battery. I hate VATS and I'm going insane.
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Struggling with VATS bypass 
