Hi, I’ve got an 1990 firebird v6 that will not run. I’ve narrowed the issue down to the security system. I’ve done a ton of reading in the forum about the vats system and how it controls whether or not the fuel injectors spray fuel, mine don’t. I’ve ohmed them out and that’s all good, there is fuel going to the fuel rail (I’ve already replaced the gas tank and the fuel pump and the solenoid for all that. The issue is that they installed an aftermarket security system in the car and removed the passkey module and the starter relay, it all goes through a module they added, I can’t find a wiring diagram that helps me figure out what wires could be plugged into the aftermarket system and there’s no way for me to turn it off. I have no issues with the starter, I believe they just jumped it under the dash. Is there a way for me to test if the module behind the hvac duct is still there? Can I do something that doesn’t involve getting a new PROM? I really don’t want to take the dash apart to get in there. I don’t know if the added security system takes place of just the passkey or both. The system has 12 wires plugged into it and 3 of those wires were just tapped off. I don’t know what to do or how to reconnect the wires. I’ve done the flash codes and fixed the one code I had, now all I get is the one that says the test is engaged.

 

It's almost impossible to guess what any given aftermarket alarm system might do to your car if it failed.

Best thing to do is, identify what wires are factory, and what are part of the alarm; remove all the alarm ones; and hook the factory ones back up like they were. Splice them back together if they're cut, etc. You may need the FSM for your car to get all that right; again, all of those alarms are different, there's no way out here that anybody will know what to do, unless maybe you can tell us what brand & model it is, then somebody might be familiar enough with it to help.

The original VATS system in your car relies on a resistor in the key. The key has to match the module; there are about a dozen different values that the resistor can have, only one of which your module will be satisfied with. If the add-on thing disabled that, or altered it in any way, it might be possible to substitute in a resistor that's not part of the key, which will make the module happy at all times. It's not impossible that the aftermarket thing is in that circuit somehow, such that it replicates the VATS function; in which case removing it and restoring the wiring to the factory will fix it. No real way for us out here to know that though. You'll have to do all the digging inside your car yourself.