Swapped 305 out to 350. Won't start with key have to bypass ignition

The security, antitheft, or passlock light is a visual indication that something in the car's antitheft system is failing. In most GM cars and trucks there is a hidden system that most people are unaware even exists. From the moment you put your key in the ignition, there begins a constant line of communication between your key's security chip or transponder, to the ignition's lock cylinder, and then to the car's TDM (Theft Deterrent Module). These 3 parts are in CONSTANT communication. If the key is in the ignition, then these parts are sending signals to each other. The security light illuminates when that signal gets broken, even just for a second. When the signal breaks, the car misinterperates this as an attempt at theft and goes into antitheft mode. The car thinks its being stolen or hotwired because it is not getting that signal from YOUR specific key. This is why the security light turns on and shuts down your vehicle.
This link may help you find ways to bypass this or fix it yourself.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

I have this same issue - I've researched it to death. I've been told it everything from the BCM (body control module aka computer) to a bad ignition switch to a loose ground. The cost to getting it fixed runs into the hundreds of dollars. Fortunately it comes and goes and is not a permanent fault on my Impala. The security indicator lights because the computer thinks the car is being stolen. I swapped keys and it does seem to help but it still crops up now and then. The easy solution is to turn the key to the off position and (this is very important) wait no less than 10 minutes. Turn the key and your vehicle should start. 10 minutes is the time it takes the system to reset. During that 10 minutes reset period don't open the doors or turn the key at all. Hope this works for you as it continues for me.

The security light is a visual indication that something in the car's antitheft system is failing. In most GM cars and trucks there is a hidden system that most people are unaware even exists. From the moment you put your key in the ignition, there begins a constant line of communication between your key's security chip or transponder, to the ignition's lock cylinder, and then to the car's TDM. (Theft Deterrent Module) The TDM is what tells your computer that the correct key is being used and that it is "OK" to allow the vehicle to start and run. These 3 parts must be in CONSTANT communication. If the key is in the ignition, then these parts are sending important signals to each other. The security light illuminates when that signal gets broken, even just for a second. When the signal breaks, (normally due to a failing/broken part) the car goes into antitheft mode. The car thinks its being stolen or hotwired because it is NOT getting that signal from YOUR specific key. There is where the security light turns on and shuts down your vehicle. So basically, if that light is on, your system has some sort of failing part. This can start as an intermittent "no starts", to your vehicle not running for days at a time, to the vehicle NEVER starting again. The problem is electrical and computer based, so don't count on an easy reset button, or the problem fixing itself. The hard part is isolating which part is the problem. You can spend a thousand dollars through a mechanic very easily. I have had great luck with bypassing the entire system. This way the problem will never return. CAN'T ever return and can be done yourself at a much cheaper cost. Read through this link very carefully. You'll find alot of information and pictures, along with ways to help you fix this.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

Is the security light on or blinking?If not then do you have power to the starter.You can check this with a test light.You should have power when you turn the key to start.The test light should light up.Should be the small wire.I believe it is purple in color.If the security light is on then you will have to get the codes to see what is causing the no start.Hope this helps.Good luck.

The security light is an indication that something in the car's antitheft system is failing. One of these days, you will try to start your car and it won't start. There is a line of communication between your key's transponder, (hidden in the plastic head, you wont be able to see it) the ignition's lock cylinder, and the car's TDM (Theft Deterrent Module). These 3 parts are in CONSTANT communication. If the key is in the ignition, these parts are sending signals to each other. The security light illuminates when that signal gets broken, even just for a second. When the signal breaks, the car goes into antitheft mode. The car thinks its being stolen or hotwired because it is not getting that signal from YOUR specific key.

So now on to the bad news. When that light is on, the car will do one of two things. It will either turn off the starter or the fuel injectors. (to prevent theft) Im guessing that your car does the starter or else your car would have died whe the security light turned on. The hard part is diagnosing which part is failing. You can spend up to a thousand bucks swapping out the parts yourself, or take it to a dealer and let them rob you blind. Ive had great luck in just bypassing this entire system permanently forever. Check out this link. Its full of info,pictures,and links to help you with this problem

http://vatspasslockpasskeysecurityhelp.yolasite.com/

you can not bypass the security in that car, it is built into the main computer, they have problems with the ignition switch screwing up and the only way to start it while the light flashes is to turn the key to ON but don't crank engine, leave on for 10 to 15 minutes until light goes out then start car.

Hi.

A problem with the theft system has triggered the service test system light.

The best thing to do is going to the nearest dealer place and performing a theft system learning, some theft system malfunctions may end up with the car not starting.

Here the learning procedure:

1. Pit ignition ON keeping engine OFF.
2. Turn key to start the engine, then release the key to ON position (the car will not start).
3. Wait for the security info to end. It will last about 10 minutes.
4. Put ignition OFF the ignition, and wait 5 ten seconds.

Repeat steps 1 through 4 two more times f 3 times in less than 30 minutes

The vehicle will be ready to relearn the Passlock Sensor Data Code next time the ignition is turned from OFF to START (crank )
Turn the ignition OFF before attempting to start the vehicle and start the engine so that the vehicle will learn the Passlock data again

You may need to jump the battery or to use a charger as the procedure may drain the battery.

If that does not work go to the dealer. They will scan and reset security system and perform a re learning using a diagnostic tool.

Im guessing you tried to bypass the key in the ignition/steering column. This is ok unless the actual problem was in the TDM (theft deterrent module) In this case, the 2 wire bypass does nothing. There is another way to bypass this. Check out this link for tons of info and some DO IT YOURSELF options. Ive done several key bypasses and tons of full bypasses. They both work well, it just depends on what part is failing. I think you need the full bypass to eliminate that TDM.

http://vatspasslockpasskeysecurityhelp.yolasite.com/
1994-1999 Eighty-Eight

If you hear relays clicking sometimes and the jeep won't start, at those times, is the check engine light illuminated on the dash, or not? If no check engine light is on the dash, at times when the jeep won't start, your ecu is in need of repairs. The ecu sends power to the ignition and fuel relays and when the ecu starts to malfunction, the relays usually start clicking.

• The only way to try to start a car by bypassing the ignition is to pop the hood and jump start the starter (where the big red power feed wire is connected) to the positive terminal on the battery. If the vehicle is PATS security protected I don't think this will do any good because when a PATS key malfunctions the cars ECM shuts down and the car won't go anywhere until a functioning PATS key is inserted into the ignition.

Regards, Tony