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Discussion Starter #1
Hello guys, this is my first post on the forums, and unfortunately it isn't a pleasant one. A little backstory on me and the situation that brings me here. I am a locksmith and this isn't my first dance with Chevy Vats, Passlock and Passlock 2 systems, but it just so happens that this time, on my own vehicle I am having the most trouble. I have a 2004 Chevy Impala former police vehicle that my roommate gave to me when it broke down. It's been a while since he had it but if I recall the car became increasingly difficult to get to turn over, he had to do the 10 minute wait more and more frequently until the car simply would not start anymore. He went off to be a trucker and was going to scrap the car to not have to worry about it and I convinced him to give it to me because I love this thing and don't want to see it go to the scrapper.

I started by doing all the things I knew he had done. 30 minute relearn procedure a multitude of times. New Ignition Switch. New Ignition Cylinder Keyed to original key (new factory originated key, not a worn copy) inside original cylinder housing, 30 minute relearn. The new ignition cylinder in new housing, 30 minute relearn. None of this worked. So I let it sit for months and months until I decided I wanted to get it going.

This Saturday morning I had it towed to work bright and early and got started. I bought a brand new battery and installed it. I read the resistance coming from the thin yellow wire (passlock signal) to the black (ground) and got 596 ohms, I grabbed the closest resistance Vats Key, a #12 Vats key (601 ohms), cut the chip out, soldered leads to it and spliced it into the wires interrupting the signal from the black module on the cylinder housing (we call this the candy coated shell) to see if this would satisfy the passlock system. If the system was working correctly this should have been close enough to allow the vehicle to start, but it did not. Next I tried to program the new resistor using the 30 minute relearn and it did not work. Occasionally I can get the security light to go off after 1 of the 10 minute intervals, but it won't go/stay off at the end of the 30.

I then tried other various things I had seen on YouTube that I had not wanted to resort to such as pulling the BCM fuse out and putting it back and trying to start it. None of them worked. I then dove into it with our Autel programmer/scan tool. There is no off board programming procedure for these as you may know, but I did try "reprogramming" the BCM to the car. Changed vin to a different Impala Vin, changed it back, entered point of sale and options successfully and then tried to relearn the resistor as well as the candy coated shell. No Luck. However: after I cleared the codes the security light would sometimes blink as opposed to come on and stay solid, which was a change.

Tomorrow I am waking up early before work and going to buy a BCM from a local salvage yard just for testing purposes. I am also going to go check to make sure my starter cranks when the relay is grounded as well as some of the various grounding points I had seen referenced in various YouTube videos. I am also going to order a resistor kit so I can try to program an actual 2200 ohm resistor which is recommended in most of the videos I watched. I've done a lot already and I'm only just getting started as I rather enjoy the satisfaction of nailing down complex problems like this.

And so I am here to pick all of your brains. I appreciate your time guys and look forward to your feedback. I don't mind any critiques on what I've done so far as long as it comes paired with some useful advice. I'm here to learn. Thanks so much in advance guys.
 

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I read the resistance coming from the thin yellow wire (passlock signal) to the black (ground) and got 596 ohms, I grabbed the closest resistance Vats Key, a #12 Vats key (601 ohms), cut the chip out, soldered leads to it and spliced it into the wires interrupting the signal from the black module on the cylinder housing (we call this the candy coated shell) to see if this would satisfy the passlock system. If the system was working correctly this should have been close enough to allow the vehicle to start, but it did not.
The resistor bypass trick worked on the older systems where there was a resistor built into the key. Both my 91 Bonneville and 99 Lumina had this setup.

On the gen7 Impalas (2000-2005), for security, in lieu of the resistor, there is a Hall effect sensor in the ignition key assembly. It detects the presence of the key inserted into the cylinder. As I recall, there are three small wires to it: black, white, and the yellow one you mentioned. If the key is not detected, the SECURITY message comes up on the instrument cluster, and the engine won't crank.

The Hall effect sensor works sort of like a resistor, but its resistance varies with the presence of ferrous (metallic) materials nearby - ie, the key being inserted. So using an ohm meter to determine a resistance value isn't reliable.

A technical service bulletin (attached) was issued which pertains to this sensor. The connectors at the BCM (where the yellow, black and white wires connect) develops some added resistance in the contacts, presumably due to galvanic corrosion, resulting in a mis-read of the Hall effect sensor thereby causing the SECURITY light and no-crank condition.

In brief, the TSB says to clean the contacts, WITHOUT damaging them. The easiest way to do this, with the battery disconnected, is to remove and re-insert each of the three connectors a few times. This will help wipe restore good contact for the pins.

In your case, you will also need to undo the wiring change you made for the sensor, and restore it to stock configuration.

There may be other workarounds for this, but I don't have any experience with them. If was going to try something, I would try taking the sensor out of the ignition assembly, and taping a key to it so that it always sees the same reading from the sensor. But that may introduce other unforeseen issues such as the car thinking the key was left in the ignition causing dinging when you open the door.

Good luck with it. Let us know how it works out.

HTH.

Doug

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Discussion Starter #3
The resistor bypass trick worked on the older systems where there was a resistor built into the key. Both my 91 Bonneville and 99 Lumina had this setup.

On the gen7 Impalas (2000-2005), for security, in lieu of the resistor, there is a Hall effect sensor in the ignition key assembly. It detects the presence of the key inserted into the cylinder. As I recall, there are three small wires to it: black, white, and the yellow one you mentioned. If the key is not detected, the SECURITY message comes up on the instrument cluster, and the engine won't crank.

The Hall effect sensor works sort of like a resistor, but its resistance varies with the presence of ferrous (metallic) materials nearby - ie, the key being inserted. So using an ohm meter to determine a resistance value isn't reliable.
It is interesting you say this because interrupting the circuit with a 2200 Ohm resistor, or adding it in line with the candy coated shell and relearning seems to be a rather successful method for a lot of people. I know this doesn't work most often than not with the Passlock 2 System which employs the Circle Plus and PK3 Transponder keys.

A technical service bulletin (attached) was issued which pertains to this sensor. The connectors at the BCM (where the yellow, black and white wires connect) develops some added resistance in the contacts, presumably due to galvanic corrosion, resulting in a mis-read of the Hall effect sensor thereby causing the SECURITY light and no-crank condition.

In brief, the TSB says to clean the contacts, WITHOUT damaging them. The easiest way to do this, with the battery disconnected, is to remove and re-insert each of the three connectors a few times. This will help wipe restore good contact for the pins.
I am definitely going to read that bulletin and follow the instructions within.

In your case, you will also need to undo the wiring change you made for the sensor, and restore it to stock configuration.

There may be other workarounds for this, but I don't have any experience with them. If was going to try something, I would try taking the sensor out of the ignition assembly, and taping a key to it so that it always sees the same reading from the sensor. But that may introduce other unforeseen issues such as the car thinking the key was left in the ignition causing dinging when you open the door.
I did take the resistor out of line and put the harness back as it was Saturday when I had exhausted trying that as an option. I will try taking the sensor out and taping a key to it as you said to see if it makes a difference, however I'm cautious to do so because my housing is a brand new OEM Strattec housing and I don't want to damage it. I went ahead and ordered a BCM 10350647 from a local scrapyard and I'm picking it up tonight to use for diagnostic purposes. I'm gonna work on it when I get off work tonight and I'll report back.
 

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I will try taking the sensor out and taping a key to it as you said to see if it makes a difference, however I'm cautious to do so because my housing is a brand new OEM Strattec housing and I don't want to damage it.
Never mind. I misunderstood your earlier comment about cutting "the chip out". Leave the sensor in the switch assembly.

If you can splice a resistor between the yellow and black wires to defeat the system, and make it work, go for it.

That said, with the sensor properly installed in the switch assembly, and a good connection of the 3 wires to the BCM, it should work fine without it.

I've attached a schematic of the circuitry for the key sensor, but it has too many unknowns - no resistor values, no indication of what's in the security sensor box - to give a clear indication of what is required to defeat it.

The Hall effect causes the resistance in the sensor to change when the key is inserted. So I would expect the BCM to look for different resistance values - key in, key out. If it doesn't mind seeing the same value all the time - key in - and you can insert a value it likes, then that will be a successful defeat.

As for the measured 596 ohms, I think determining the right value is more involved than just ohming it out. The 5V on the yellow wire will throw off the meter measurement. And, looking at the drawing, it appears the BCM may sweep the voltage on the white wire, which will also affect the measurement.

It may be that putting 2200 ohms between yellow and black works. You may need to cut the yellow wire between the added resistor and the lock cylinder so that the sensor signals coming out pin A don't throw off the signal seen by the BCM.

Doug

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Discussion Starter #5 (Edited)
Thank you for that schematic. From my understanding when you put a key in and turn it, this is when the vehicle sends a signal checking for a specific resistance. (GM seems infatuated with using this for their security systems. You think they'd have learned). So when I read the resistance it is with yellow wire open, the black wire closed but bare and the white wire untouched. I put the key in the on position and check the resistance between yellow and black coming from the car and the yellow wire from the ignition out of the circuit. And get approximately 601 ohms consistently. Now if this is what the vehicle is supposed to have or not, I have no clue but GM used anywhere from 500 to 3000 across the various shells so it would seem legit.

However I have abandoned that notion for now or at least until my proper resistors arrive. I put the harness back to rights and put in my used BCM. I programmed in the VIN and it would not take SCM, Point of Sale or Options as the BCM is secured. This should still allow the vehicle to do the relearn and start but I would lose airbags and the radio. Which is fine, I bought this BCM just for testing. I did the relearn and at the end of the third cycle the security light went out but it would not start. Real bummer. And after taking the key out and putting it back in a few times the security light came back on. I tried jumping the crank relay while the security light was out and had no luck. Another bummer.

There are really too many variables involving the new ECU to really pin anything down but now I'm curious if this may be a problem in the PCM or ECU. As we speak I am trying the relearn procedure on the original BCM to see if I can replicate the light going out but not staying off after the key has been turned a few times. I just finished the first 10 minutes and I'm on the second. If the problem persists I am going to try another cylinder housing just to see.

I'm a little dejected from my lack of progress after hours of work and even more hours of research. Short of buying a totalled donor car I'm not sure what else to do. I'm tempted to tow it to mechanic and let them have at it and tell me what's wrong. I have a mechanic I trust but he isn't cheap and the whole point was just to get this beater going, drive it for a bit and then sell it.
 

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Discussion Starter #6
Alright, so here is what I got. It passed the relearning and the security light went out and stayed out for a bit. If I turn the ignition off and on a few times weather I crank it or not, the security light will come back on. I check it with my scanner and there are no codes. I take the key out and put it back in and turn it on. It cycles through all the battery indicator, then security, then back to battery and stays there. No security light. Any ideas? I am not sure exactly what is happening but I'm no longer sure this issue is on the passlock system, or if something else isn't affecting it.
 

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Alright, so here is what I got. It passed the relearning and the security light went out and stayed out for a bit. If I turn the ignition off and on a few times weather I crank it or not, the security light will come back on. I check it with my scanner and there are no codes. I take the key out and put it back in and turn it on. It cycles through all the battery indicator, then security, then back to battery and stays there. No security light. Any ideas? I am not sure exactly what is happening but I'm no longer sure this issue is on the passlock system, or if something else isn't affecting it.
If it's not the security thing, the next step is to ring out the ignition-to-starter path. I've attached a drawing for the starter. (Also attached is the full security schematic - I meant to include it with my earlier post.)

I think my first test would be to remove the starter relay (CRANK RLY) from the underhood fuse box and jumper between C8 and B10. That should cause the starter to crank. That will tell us if the problem is upstream of the relay, or downstream.

[Edit] If the fusebox pins are not marked, I think C8 corresponds to relay pin 30, and B10 to pin 87, as marked on the bottom of the relay.

Doug

2004_impala_starter_engine_cranking_CAVR1XCQ.gif

2004_impala_security_full_CAZ6PKXR.gif

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If it turns over but never starts...

Is your fuel pump priming? Put the back seats down and pull the carpet apart where it overlaps and there is a magical portal to the fuel pump. If you can't hear it priming get a multimeter and a friend and see if there is voltage in the plug for a couple seconds right after the key is turned. I wrassled with what I thought was a security issue for days until I found out it was my new but cheap fuel pump. Our cars have Passlock III, as others may have mentioned. The resistor trick doesn't work. Good luck!
Jake
 

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Discussion Starter #9 (Edited)
Well my car wouldn't crank at all, and would not relearn the ignition cylinder forever until I finally replaced the BCM and the Ignition/Housing with an OEM strattec unit. Then I was getting power to the starter relay but no crank. I had the starter tested and it failed. I ordered a new starter, it arrived tonight and I put it in. Then it cranked up and ran first try after sitting since last August. Nice!

I actually am doing a write up/YouTube video on the subject because after all the time I've put into it I'm finding that there isn't a whole lot of conclusive info out there.

Now I've learned that if I hit a bump my headlights will both bop out and back on quickly, and the blinkers don't work at all but I'm going to make a whole new thread on that to keep this one concise for anyone who stumbles upon it with the same problem. I'm going to write a long post about my trouble shooting procedure later.
 

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Glad you got it running. Good luck with the lights and blinkers. I'm putting together the pieces of dash panel that fell apart in my hands when I removed it to replace the ignition 🤷‍♂️ Hey this is fun, right?!
 

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Discussion Starter #11
It's definitely a process, but I love learning, a good challenge and fixing things. So this is a win win win.
 

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I can tell you that my ‘02 started “not starting” with the SECURITY message in September of 2007, at 97,475 miles ... so 5.25 years into ownership after purchasing new. Then it would happen a couple times a year every year (but sometimes just a message and it still started OK) until ... it hasn’t happened now in almost FOUR years!

And I never did anything to“fix” the problem because I wasn’t convinced that any of the “solutions” were definitive.

So - how is it that the problem has just gone away on its own?

The only thing that’s “changed” is : my wife passed the car to my son (who drove it his senior year of high school and never had the problem), and then it came back to me (in 2016). I drive it back and forth to work 4 days a week, 12,000 miles a year. It’s not just sitting around, yet ... no more SECURITY message, and it’s always started at least twice a day, or more if I stopped at a store on the way, or back. It also has never been touched by a mechanic (I do all maintenance myself). And I’m only mentioning that to say that no mechanic has ever done anything to the vehicle that might’ve fixed the problem without my knowledge. It’s also been driven in the exact same environment all these years.

I don’t know the answer. But it would appear that all these suggested workarounds are not the answer. In fact, people have implemented them only to see the problem come back again - that’s why I never bothered to do any of them (cutting the yellow wire was the only one I got close to doing).

Oh - and I also haven’t had the fix for “unintended ignition key rotation” implemented, either. I get into the vehicle every morning and sometimes the key “sticks” or “jams” ... such that it won’t turn enough to start the engine, but I just jiggle it while turning at the same time and it ends up working. Been doing this for at least four years now. Doesn’t seem to be getting any worse.

So ... I’ve done absolutely nothing ... no key change, no cylinder change, no resistor or BCM modification for this SECURITY “no-start” issue ... and I haven’t seen it now in FOUR years!

How can that be?? I don’t know...
 

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The only thing I have to add is this, from the Chevrolet 2002 Impala, Monte Carlo Service Manual (the hard copy the dealer shops would have):
20200503_215119.jpg
 
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