Hey everyone,
Im having a problem with my 2005 monte carlos security system. This car has been sitting for a little over 3 years. someone tried bypassing the security system straight to the starter so there is a button for starting it instead of a key. I bought a new lock cylinder for it and tried bypassing it with a resistor and for some reason when the battery was connected the resistor was reading 0.0 ohms. The car still didnt start after the bypass however, i watched a yt video and unplugged the bcm fuse on the drivers side panel and it started with it out and i plugged it back in and it kept running. does that mean my bcm is bad and i need to replace it? I dont know much about cars and i need some advice. thank you!

 

As this apparently has a bunch of electrical modifications, do you have any kind of wiring diagram of what was added?

My gut feeling is that something was broken in the factory system, so someone added wiring to work around whatever broke but now the aftermarket addition has also failed causing a no start (so its really 2 failures in one).

If it were me, and you had no wiring diagrams for what was done - Id tear it all out and put it back to stock. Then you can follow the factory wiring diagrams and diagnostic tree to uncover the problem and fix it (without all of the added stuff).

The problem is electrical diagnosis is hard enough with all of the OEM repair data available. When you've got more wiring bypassing and modifying the factory system, its going to make the process a whole lot harder as its now fully up to you to figure out what signals are going where + whats missing.

 

Sadly, I do not have the diagrams but the button is still functional. What I think what happened was somebody couldnt get it started tryed bypassing it with the resistor method ( black and yellow wire were cut, white still attached) and they mustve did it wrong causing the car to not start. They then straight up put a button to the starter so it would “bypass” the security. Im guessing it worked for the time being however, it quit working after the battery went dead or something and they unplugged it resetting security again?

So, when i started working on the car there was a blown fuse for the fuel injectors which was the reason why it wouldnt start. Got that replaced and it started and died which was the result of the passlock 2.

i ordered a new lock cylinder because the original one was missing? I hooked all the security wires back up to the clip leading to the ignition and to no avail still no start. I tried the security relearn everyone talks about. Security light stayed on after 15 mins even with the door closed tried this about 5 times.

With the bypass hooked up in its current state and still with the push start button, removing the bcm fuse and starting made it run and it ran on its own without dying. Now im stuck because is it a bcm issue or like you said, a wiring issue. Also when it ran the security light was still on.

the car is a electrical nightmare, foglights stay on and parking lights when battery is connected. Someone also stole the aftermarket radio that was put in it. I have no clue if that would contribute to the problem.

Currently my 2 options are to either try and track down the wires that are messed with and like you said try and remove the wiring directing to the starter and hook it back up to the ignition. (Idk if that would work because i dont have the original lock cylinder) but is worth a shot.
my second option would probably be to try and replace the bcm because for some reason some electrical stuff stays on when its not supposed to (maybe bad wiring) then get it programmed by a dealer ship

I appreciate the advice and i will definitely use it as a troubleshooting step. If you having anything else you would like to tell me that would be much appreciated thanks!