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DELCO NERD
1993 Pontiac Firebird Trans Am, LT1 5.7L V8
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If the "SECURITY" light is flashing during cranking and the car won't start, the PASS-Key II system is detecting a tamper. For whatever reason, the system is not reading the correct resistance from the pellet in your key. Am I describing the symptoms correctly?
 

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Discussion Starter · #22 ·
If the "SECURITY" light is flashing during cranking and the car won't start, the PASS-Key II system is detecting a tamper. For whatever reason, the system is not reading the correct resistance from the pellet in your key. Am I describing the symptoms correctly?
Yes actually I do recall it doing that upon thinking about it for a while. I also got a call from my mechanic today and he suggested it could be the camshaft position sensor acting up too because admittedly I did replace it with an OTS part (before I knew better about sticking to DelCo stuff). Does that sensor have anything to do with the issue at hand here if anyone knows? I would not suspect it is an issue as I did not have any codes for the sensor (I did scan it with an OBDII reader) but what do I know?
 

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1993 6-spd T/A - 1996 C4
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A defective Crank Position Sensor most certainly can prevent the engine from starting, but that has nothing to do with VATS. There are 2 scenarios with VATS regarding a flashing SECURITY lamp, and both point to a defect in the circuit preventing the key from being seen. Which scenario fits? We can't answer that. Read on, and pay special attention to what I have emphasized. IF, BIG if, the SECURTIY lamp has always flashed and the engine ran, sure, consider the crank position sensor. A lot of aftermarket electronic components these days are garbage and defective out of the box or have a high failure rate. However, if the flashing began with the no start condition, the condition and lamp are related.

You have 3 paths available
  • Download the Factory Service Manual (free) and diagnose the crank position sensor / Read shbox's VATS page and diagnose VATS.
  • Pay your Mechanic to diagnose and resolve it.
  • Start randomly replacing parts until you get the engine to fire.

From the authority on VATS (shbox): 4th Gen LT1 F-Body Tech-PassKey/VATS

Abnormal Operation

If the key pellet is the wrong value, the TDM will not send signals to allow the starter to engage or fuel to the engine. The TDM will shut down for ~3 minutes and the SECURITY lamp will remain lit with the key ON or OFF. When the ~3 minute timer has expired and the key is cycled from OFF to ON, the TDM timer is reset. If you try a key with the correct pellet value, the engine should start and run. SECURITY lamp should be off. If there is still a problem with reading the key, the TDM will light the SECURITY lamp and start the ~3 minute timer again.

If the sensing contact circuit is open or shorted (cannot read the key) or a defective key is used at the time the ignition is turned ON, the SECURITY lamp will flash at a rate of once per second and the engine will not start. No three minute lockout will begin.

The SECURITY lamp will also flash at once per second if a new, unprogrammed TDM is installed and there still is a defect in the key reading circuit. The engine will start in this condition, though.


The lock cylinder circuit is continuously monitored. If a fault lasting 1 minute is detected, the SECURITY lamp will light. If the fault then goes away for 1 minute, the lamp will go back off.

If the system detects a fault with the lock cylinder circuit after the engine is already running, the SECURITY lamp will light. The engine will be able to be restarted. This is called “fault enable mode”. (The system saw a good reading from the key at one point during a previous ignition cycle before the failure. So, it considers it a problem and not someone trying to steal the car.) When in fault enable mode, PASSKey protection is disabled until the problem is repaired. Once repaired, the SECURITY lamp will go out about 1 minute after the key is turned on. Fault enable mode will not shut down the engine while you are driving.



The Factory Service Manual will assist you in diagnosing the Crank Position Sensor. You should only need a $10 Multi-Meter (volt-ohm meter) for this. Start here if the SECURITY lamp always flashed before but the engine still started. Otherwise, the "key sensing circuit" is open, as in, something isn't making contact.

While both scenarios point to a "problem in the circuit", they are both key related. The little "pellet" in the key is nothing more than a resistor, and it would in my opinion be extremely rare for a resistor to just die electrically in a manner that creates an open circuit. ...but if you probe it with the multi-meter and get no reading what-so-ever, there you go. Dead resistor. Using a multi-meter and the information at shbox, this is easy to determine.

It is more likely though that the resistors contacts on the key have worn down so far they physically do not make contact with the ignition barrel. No key contact with the barrel would be an open circuit as the key completes the circuit. A worn ignition barrel that can't contact the key? Same thing.

Installed something aftermarket and rooted around in the dash? Maybe the connector for the ignition barrel came loose and after some time and vibration, open circuit. Broken wire? Open circuit. Regardless of which "flashing security lamp" scenario you fall into, the Theft Deterrent Module can not "see" the key's resistor. ...that is the thing to take away here. While in scenario two, the engine starts, the key's resistor is still not completing the circuit for whatever reason. Hell, you could have bought the car with scenario two being a thing and over time progressed into scenario one. Hard to say.

VATS seems like an intimidating system and most belittle it, but it's not complicated at all. Read over all the VATS information at the shbox site and follow the links. The mystery and magic of VATS quickly disappears. It really is a straight-forward and easily diagnosed system once you get past the intimidation of it. ...and the quickest way to get over it is to learn about it.

If you read though all the VATS information, not only will you be able to diagnose the system, you'll immediately know how to "bypass" it very cheaply and easily should the culprit be the key or ignition barrel. That is if you want to bypass it. Should you want to keep the VATS functional, you'll at least know what you need to replace.

As to no codes for the crank position sensor, unfortunately, it is possible for things to fail without setting a code. Not very likely with that particular sensor, but not unheard of either. This is why I point you to the Factory Service Manual. It will have an easy to follow flow-chart to diagnose the sensor. Where you should begin looking first though hinges on if or if not that SECURITY light was flashing before the no-start condition. Either way, it's easy stuff if you have the right tools and resources. No need for a mechanic unless you don't want to be bothered with it, but having a scan tool and changing the crank position sensor yourself suggests to me that you do want to learn and take care of this, so grab that factory service manual regardless. Even if you don't need it this time around, you'll appreciate having it next time when you do.

...and if you don't have a multi-meter, get one now, because if it has a wire going to it then a multi-meter is required to diagnose it. The Factory Service Manual and a Multi-Meter really are the two most valuable tools you can have if you want to keep these cars going. ...one of them is free, and the other is under $10. No excuse not to have them.

Good Luck!
 

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Hopefully he actually reads our responses. I told him to download the factory service manual in post #2, and told him to read Shoebox's PASS-Key writeup in post #16. I've given up trying.
 

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Discussion Starter · #25 ·
Hopefully he actually reads our responses. I told him to download the factory service manual in post #2, and told him to read Shoebox's PASS-Key writeup in post #16. I've given up trying.
Yeah I'm reading your responses, and did download the service manual and did bookmark the VATS bypass page. What has been going on I haven't been able to duplicate in the past few days well really because I haven't been driving the Firebird all that much to be perfectly honest. I did do some short around town drives and it seemed to do okay though, although I did get a SES light with a P0341 yesterday night which points to the camshaft position sensor. Thankfully I have an ACDelco one on order to replace the Chinese one currently in the car.
 

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Discussion Starter · #26 ·
Okay so I've returned to probably the dismay of many (that's sarcasm) because today was my first substantial drive if you could even call it that. I drove around my town a little bit and everything was okay but after I made a turn the car essentially stalled on me, but I was able to get it into a parking lot and it started up roughly at first after putting it in park and turning off everything that could draw a load (AC, etc.) but after turning it off and starting again it started normally and I was able to get home with no issues. I'm not sure if it's relevant to what is going on, but I figured it was worth reporting. Did not have an SES light, and did scan for codes and none came back. The intersection where it stalled was slightly inclined but not by much, however it seemingly stalled when I turned onto a side street (which was level) and that's where everything happened. Is it possible this is tied into the issue that was originally described, or could something else be at play here?
 

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When you are running the A/C it puts load on the engine. When you turn the steering wheel the power steering pump puts load on the engine. To prevent stalling the engine, it’s the IAC valve's job to increase air flow to handle the added load and maintain RPM. As I recall from the earlier data log(s?) the IAC was often maxed out at 160 counts, even at idle in many instances.

That said, my suggested cure of opening up the throttle blades with the stop screw didn’t work. I'm out of ideas.
 

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1993 6-spd T/A - 1996 C4
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I'm almost wondering if your fuel gauge is reading incorrectly.

(from shbox.com) Typically, when the gauge reads:
  • way past full = full tank
  • ¾ = about half full
  • ½ = about a quarter full
  • ¼ = a couple gallons
  • E = very little on most cars (gallon or less), can be really empty on some

My fuel gauge slowly drifted out of spec because of a corrosion issue in the tail light harness, but typically, this (incorrect fuel reading) is an issue with the sending unit. Mine ran out of fuel one day sitting level at a red light showing 1/8th tank. A few months later, 1/4 tank was empty. Eventually, my gauge stayed pegged beyond full regardless of fill level so I drove by "mileage" filling up every 150-200 miles just to be sure I never got that low again. When I bought all new tail light connectors because they were corroded and causing issues with my blinkers and brake lights when the headlights were on, I noticed the copper in the harness was black when I cut the old connectors out and stripped away the wires to splice. I cut back the wires to good copper, about 8-12" each, and made my splices. This must be why they give you 2 feet of wire with every connector... Anyway, when I turned my ignition on after the repair, my fuel gauge immediately fell to the actual level in the tank, and has remained accurate since.

Point is, trusting your fuel gauge is accurate might be the problem.

I don't think fuel level (or even filter) has been discussed, so, if you fill the tank today, do you still have the problem or does it then take a few days to a week for the problem to reoccur? Seems like a head scratcher, but the most recent keywords here are stalling "around a corner" and "slight incline". ...both of which point a finger at fuel level. I'm likely way off here as Injuneer found an issue with the IAC position which has everything to do with idling, and pressing the brakes or turning the wheels load the engine to the point the IAC needs to "add a little bit of throttle" just to maintain a steady idle, but still.
 

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Discussion Starter · #29 ·
I'm almost wondering if your fuel gauge is reading incorrectly.

(from shbox.com) Typically, when the gauge reads:
  • way past full = full tank
  • ¾ = about half full
  • ½ = about a quarter full
  • ¼ = a couple gallons
  • E = very little on most cars (gallon or less), can be really empty on some

My fuel gauge slowly drifted out of spec because of a corrosion issue in the tail light harness, but typically, this (incorrect fuel reading) is an issue with the sending unit. Mine ran out of fuel one day sitting level at a red light showing 1/8th tank. A few months later, 1/4 tank was empty. Eventually, my gauge stayed pegged beyond full regardless of fill level so I drove by "mileage" filling up every 150-200 miles just to be sure I never got that low again. When I bought all new tail light connectors because they were corroded and causing issues with my blinkers and brake lights when the headlights were on, I noticed the copper in the harness was black when I cut the old connectors out and stripped away the wires to splice. I cut back the wires to good copper, about 8-12" each, and made my splices. This must be why they give you 2 feet of wire with every connector... Anyway, when I turned my ignition on after the repair, my fuel gauge immediately fell to the actual level in the tank, and has remained accurate since.

Point is, trusting your fuel gauge is accurate might be the problem.

I don't think fuel level (or even filter) has been discussed, so, if you fill the tank today, do you still have the problem or does it then take a few days to a week for the problem to reoccur? Seems like a head scratcher, but the most recent keywords here are stalling "around a corner" and "slight incline". ...both of which point a finger at fuel level. I'm likely way off here as Injuneer found an issue with the IAC position which has everything to do with idling, and pressing the brakes or turning the wheels load the engine to the point the IAC needs to "add a little bit of throttle" just to maintain a steady idle, but still.
You do bring up a valid point actually. I don't rightfully believe that is the issue as I did fill up Sunday night from a half of a tank and it's reading at past full currently, but slowly edging over to full. I'll definitely keep an eye on that though if it ever crops up in the future.


When you are running the A/C it puts load on the engine. When you turn the steering wheel the power steering pump puts load on the engine. To prevent stalling the engine, it’s the IAC valve's job to increase air flow to handle the added load and maintain RPM. As I recall from the earlier data log(s?) the IAC was often maxed out at 160 counts, even at idle in many instances.

That said, my suggested cure of opening up the throttle blades with the stop screw didn’t work. I'm out of ideas.
Well yes. I should have clarified I shut off anything that could contribute to a load on the engine after the car came to a stop. I did clean the IAC a month ago (of course using the proper cleaner and being careful) as a "why not?" thing while I had the hood open for a totally different reason and It seems to be doing fine, although going forward I will keep an eye on it.
 

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First off, I apologize if this is the wrong forum, but hi I'm a new guy here. I bought my first F car three months ago which is a 2000 Firebird. It's nothing exciting, just a 3800 automatic. It has been a very trouble free car which I quite like however for the past week and some change I have had a strange issue with the fuel pump. Before I continue I must add that the car does have a new fuel pump and filter which were installed by the previous owner prior to me buying it (I do have the papers that prove that). So anyway, the issue is after driving it for a couple hours or so, I will go to start the car and the fuel pump will not make any noise and it will not start. I first thought it was the fuel pump relay, so I replaced that and it worked file until the next day where the same thing happened again. After letting it sit it somehow started on its own. Fast forward a few more days and a three hour round drive later, I go to start the car, same thing! I must add that while it was running I had zero signs of anything being wrong, and the SES light was not illuminated as well. As far as the temperature was concerned, I would wager it was probably in the mid 90s and I was driving in daylight too. I ruled out fuses and the relay as I switched those, and I don't really think it could be the pump because if it was bad I don't imagine it would work at all and the new one only has 3000 miles on it. I've tried to research what's going on but came up empty handed because although I thought I fixed it, it's still persistent. Could someone help me figure out what on earth is going on? Thanks in advance.
Fuse underneath kickpanle..
 

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Apologies for the double post, but I brought the car home today. On the topic of the security light, it does flash when the bulb check is occurring, but does not stay illuminated when the car is actually running. My mechanic told me that for his money, it could be the pump heat sinking as Injuneer said in the first reply and that it would probably be best to swap it at some point since something could have happened that would have caused the pump to act this way out of the blue for his two cents.
Fuse in kickpanle ,camshaft ,crankshaft, ecm board
 

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Discussion Starter · #32 ·
It's been a bit since I updated you all but I'm pleased to report the issue has been solved! After a bit of researching, with help from you folks, I was able to do some troubleshooting and found out the issue this whole time was actually the crankshaft position sensor going out. I had it replaced by my mechanic (with the CASE relearn done too) and now the car is running better than ever, but most importantly the issue in the first post is completely gone. It turns out that as those sensors get old and fail, the heat causes them to not function until it has cooled down, and sometimes stalls do happen which would explain the stall a week or so back. My mechanic showed me the old sensor, and it was pretty bad, with a couple of cracks in it. Either way though the issue has been resolved so I am pleased with that. Thank you all so much for the help, and I do apologize if I was a bit of a headache to anyone.
 
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