I'm posting this for a friend..needs info ASAP...any Techs online that can give him some advice?

Thanks in advance.


2000 Chevy Silverado Z71
5.3L V8, Auto, ~70k
A couple of weeks ago while driving on the highway, the Security light on the instrument panel began to flash. I have no idea what triggered this, and it was the first time it had ever happened. The truck ran just like it should for a couple more days, but the security light would come on more frequently while driving. One afternoon it decided not to start. Later that evening it started just fine. This went on for a few more days and then it wouldn't start <again>. I pulled all the fuses relating to the ignition and ECM, swapped the fuel pump relay, and the truck started right up. However, the security light came back on while driving, and that was the last time it started. Since then I've disconnected the battery, re-pulled all the fuses, and disconnected and re-seated every wiring harness under the dash I could find, and still - it won't start. The fuel pump is priming (can hear it running in the tank prior to turning over) so I don't think this is fuel pump/filter related (when it started, it does immediately, without hesitation).
My belief is that this is being caused by the security system or possibly the Passlock II. I haven't taken it to the dealer yet, as I'm afraid they will misdiagnose the problem and I'll just be out more time and towing $$$. I've scoured the internet for articles on this one, and followed every lead I could find (reseating connectors, etc.). I bought a factory alarm bypass module that should let me eliminate the Passlock II as a problem, but am worried if I install this prior to taking it to the dealer, that they will certainly jump on this as the "problem" and not work with me beyond that point.
I'm stumped. I'd like to completely disable/remove the security system completely if possible, but can't find any docs to that extent anywhere...
Thanks in advance for any help,
Scott…

anybody?

You could try a relearn. It consists of turning the key on and leave it on for 30 minutes or something to that effect. Let me look it up and get back to you.

The other thing that could be going on is a bad sensor that reads the key.

30 Minute Learn Procedure
1-Turn ON the ignition, with the engine OFF.
2-Attempt to start the engine, then release the key to ON, vehicle will not start.
3-Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
4-Turn OFF the ignition, and wait 5 seconds.
5-Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes, the vehicle is now ready to relearn the Passlock™ Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.

Important
The vehicle learns the Passlock™ Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.


6-Start the engine. The vehicle has now learned the Passlock™ Sensor Data Code and/or password.
With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100 ignition cycles.

Kind of funny, worry about taking it to the dealer for misdiag, but come on here asking the same techs that work at the dealer how to fix it.

he has tried the relearn and recently just installed a bypass just to get it started again and it did the same thing with the bypass installed. he said that after removing the bypass and soldering all connections back it now started with both keys...BUT...how long before it will quit again when he needs it? He said the sensor was putting out a consistant amount of Impedence. I suggest trying a new key first, but dont' know if that will work or not. he is leaning towards the ingition switch right now.. any other tips/clues?

Kind of funny, worry about taking it to the dealer for misdiag, but come on here asking the same techs that work at the dealer how to fix it.

the guys that get on here are Gods compared to some of the techs we have locally.

Just messing with you.

I work next to some of those guys, I know.


If you can have someone check for a pass lock code at least.

Here is a list of codes

<TABLE cellSpacing=0 cellPadding=1 border=0><TBODY><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=599062&evc=sm&pubid=148&cellId=59290&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC 25/35 Security Indicator Status (http://service.gm.com/servlets/BlobShtml?ShtmlFile=599062&evc=sm&pubid=148&cellId=59290&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545134&evc=sm&pubid=148&cellId=59271&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B0688 Security System Indicator Circuit High (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545134&evc=sm&pubid=148&cellId=59271&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545135&evc=sm&pubid=148&cellId=59272&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B2947 Security System Sensor Power CKT Low (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545135&evc=sm&pubid=148&cellId=59272&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545140&evc=sm&pubid=148&cellId=59273&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B2948 Security System Sensor Power CKT High (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545140&evc=sm&pubid=148&cellId=59273&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545142&evc=sm&pubid=148&cellId=59274&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B2957 Security System Sensor Data Circuit Low (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545142&evc=sm&pubid=148&cellId=59274&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545147&evc=sm&pubid=148&cellId=59275&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B2958 Security System Sensor Data Circuit High (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545147&evc=sm&pubid=148&cellId=59275&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545150&evc=sm&pubid=148&cellId=59287&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B2960 Sec Sys Sensor Data Incorrect but Valid (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545150&evc=sm&pubid=148&cellId=59287&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545154&evc=sm&pubid=148&cellId=59319&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B3031 Security System Controller in Learn Mode (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545154&evc=sm&pubid=148&cellId=59319&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545155&evc=sm&pubid=148&cellId=59276&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC B3033 Security System Indicates Tamper (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545155&evc=sm&pubid=148&cellId=59276&mspsdsubkey=960) </TD></TR><TR><TD vAlign=top align=right width=35>http://service.gm.com/images/bdocument.gif (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545160&evc=sm&pubid=148&cellId=59270&mspsdsubkey=960) </TD><TD vAlign=top align=left>DTC C0559 EEPROM Checksum Error (http://service.gm.com/servlets/BlobShtml?ShtmlFile=545160&evc=sm&pubid=148&cellId=59270&mspsdsubkey=960) </TD></TR></TBODY></TABLE>

If he just installed a resistor style bylass (which it sounds like he did) it will not solve his problem. The Resistor bypass will learn the same resistance as the key provides and therefor will cause the same problem.

He should try the relearn and if he wants a back up failsafe bypass get a data bypass module such as the ones sold on www.bypasskit.com

I lent him my OBD scanner and no codes were present. I sent him the link to this thread so I'll make sure he gets on and reads all of this..

do you guys know how much those BCM modules cost?

If you can have someone check for a pass lock code at least.

just to clarify, what is the best way to get a pass lock code? do you mean just scanning the OBD port?

Need a tech II to go into the body side of the truck

Thanks to everyone so far for their help on this. I did not mean any disrespect by alluring to a possible misdiagnosis at the dealer, but I've been scouring forums for 2 weeks on this problem, and have read many "tales" of those who bought parts they didn't end up needing later. There are no returns on expensive electrical parts. :)

I had tried the re-learn procedure previously, but because of the lack of detail in the posts, I thought there was something else going on with my truck. Brian and I just got back in from working on it, so while everything is fresh in my mind, here's how it went.

1. 9/29 7:45am - After removing the universal bypass module (resistor based) on 9/28, the truck started the evening of the 28th. Decided to risk it and drive the truck to work today (chance of rain, so no motorcycle). The truck started and ran with nothing unusual occurring at start. No security light on the dash - so far so good.

2. 9/29 7:46am - I was less than .25 of a mile from my house and the security light came on the dash and stayed on, no flashing, constant on. Got to work OK, security light still on.

3. 9/29 9:30am - Brian and I walk out to the truck with his OBD reader - no codes.

4. 9/29 9:31am - Attempt to start the truck - it won't start. It seems like it actually "does start" but something kills it immediately. Think this is the case because it almost sounds like it 'knocks' right before it dies. From turning the key to it "dying" takes about 1 second.

5. 9/29 9:32am - Start the relearn procedure.
* Note - One of the reasons I did not try this before is that when I perform this, my instrument panel LCD alternates from a red battery on the display, to a blinking security light. I coudln't find anything that said this was "normal", so I thought something else was wrong, so I bailed on this procdure previously.

6. 9/29 - About 8 minutes later, the red battery indicator on the LCD stays on constant. This is good - hell, I'm almost excited at this point. Turn key "off", wait 5 seconds, attempt to start the truck - same thing as #4. Turn key "off", wait 5 seconds...

7. 9/29 - Turn key to "on" and wait about another 9 minutes - the battery light stays on constant again. Feeling good about this...

8. 9/29 - Attempt to start the truck - starts right up as though nothing is wrong.

Now this worked on the second cycle, and I didn't think I should have to do the 3rd cycle since it actually started...

Final question. The truck has started like this a few times since this problem began, and generally what happens is that #2 (above) occurs and I'm right back where I started. Can anyone tell me how to diagnose what is actually making the security light come on? Is there a way to find out what is triggering the light?

Many, many thanks to those who are taking time to help me out.
Scott...

Is it the original battery in the truck? It's a long shot but I have seen changing an old battery solve a passlock problem. Since the hall effect reading is somewhat voltage based it does make some sense that this could solve your problem. If you have a new(er) battery you can try for nothing it might be worth a try.

Also, after you change the battery do the complete relearn procedure. It won't work if you don't follow it to a Tee. That is the whole purpose of it.

I can't guarantee it is the battery that is the problem. I am only pointing out that I have seen it solve this problem once. I can't be held responsible if you go out and buy a new battery and it doesn't solve your problem. If you battery is 5 years old you should be replacing it anyways.

last I talked to Scott he is going to replace the battery this weekend and see what happens. one of us will update you soon, thanks

All -

Bought a new battery this weekend (Interstate Mega-Tron Plus) and after installing, the started without any problems at all (and without having to go through the re-learn procedure). I didn't drive it all weekend, but it started and ran fine on Monday - and there was *no* security light on the dash at any time. I thought that was a good sign. After work though, it was the same old story - turn the key, it starts, and dies. I did the re-learn procedure in the parking lot and ever since it is behaving just like it should - no security light, and it starts every time. It started on the 2nd try though, so I just let it be.

I almost don't trust that this has "solved" the problem, but it started for more than 1 day in a row, so I'm happy regardless. I used to run a car alarm installation business when I was younger, and have installed more car alarms than I care to remember, and have never seen an alarm behave like this one. The battery had never given me any indication that it was weak or going bad - and I can not see how this behavior could ever be considered a security "feature".

Thanks again for all of the help - I do appreciate it.
Scott…

its possible that the BCM is loosing the "key code". Would really need to get a Tech II hooked up when its acting up to see if it sees a valid key and still has valid keys stored in memory. I also wouldnt be supprised if its the pick up in the cylinder or something being worn throwing the resistance off changing the reading back to the BCM. you just relearned the new resistance for now maybe.

If your security light was on there has to be a code stored most likely a B2960. you need to get codes from the BCM not the PCM.

All -

First "cold" day here in Texas and the truck is back to not starting, the security light is back on the dash, and the re-learn procedure worked again. I have a couple of questions to ask at this point:

1. Cobra #3747: Since I installed a factory alarm bypass module previously, wouldn't that effectively "remove" the lock cylinder as a potential issue since the bypass would provide the resistance to the BCM? I suppose there's a chance I didn't have it connected properly, but even with it wired in, the truck behaved the identical way.

2. MikeK996: If I were to take the truck to the dealer, what do I need to ask for them to do? I would like a list of the BCM security codes, but I want to make sure I know exactly what I'm asking for so that I get the correct reading or data. Do I just tell the service manager that I'd like to get a reading of the possible security codes from my BCM from a Tech-II?

Thanks again,
Scott...

(BTW - Signed up for my own account - but the e-mail went to my house so I'll officially register later this evening...)

the bypass thing only fools computers to think there is a key in it. do you have a remote sterter in it. all you need to say is my security light came on they should aoutomaticlly scan pcm bcm and ipc for security type codes. but being somewhat intermitantly they will be history codes. but it gives them something to go on.

Really without looking at scan tool data, this is just throwing ideas around. Could have a BCM going bad also.