"Security" light on GMC truck

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  #1  
Old 02-10-03, 04:31 PM
ny25621
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"Security" light on GMC truck

Hi there,

This is my first post,

I'm working on a 2000 GMC 3500HD Classic body style truck, chassis cab, 7.4L/4L80E, etc etc.

The Security light on the insturment cluster is on, and the truck will start and run for about 2 seconds then die. I have been told by one GM dealer that the ignition switch is at fault, and by another that the ignition key cylinder is at fault. I have changed the ignition switch and the problem still exists. It is showing a P code saying that the PassKey password is not correct.

The keys in this vehicle are not of the PassKey/Transponder type, they are just regular B89 key blanks so they aren't the programmable type so the password must be kept in a different location??? Will changing the key lock cylinder solve this problem or should I look somewhere else?

Thanks for any help you may have.

ES
Butler Fleet Services
Fleet Tech
 
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  #2  
Old 02-10-03, 04:51 PM
Joe_F
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I'm assuming it is not under GM's warranty? First place I would be is back at the dealer's door letting them handle it .

Barring that, you might need access to a Tech II scanner or other GM scantool to access what's going on in there. Another thing to do would be to purchase an OEM service manual or at minimum, a 25 dollar Alldata.com subscription to give you the diagnostic trees and OEM procedures.

It's going to get expensive throwing parts at the problem .
 
  #3  
Old 02-10-03, 04:54 PM
Joe_F
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Also, there have been a few bulletins on the security system. I suggest you print out what you find at alldata.com and have a GM dealer give you copies of the full text so you know what the problem is.

Here's one I found:

01-08-56-004A SEP 01 Antitheft System - Lamp ON/Stall/No Start/DTC B2960 Set
 
  #4  
Old 02-10-03, 05:01 PM
ny25621
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Hi Joe,

Thanks for replying,

Vehicle has 41,000 miles on it, warranty is toast.

Unfortunately I can't take it back to the dealer. I do fleet service on Verizon telephone vehicles, thats what this is, it has an aerial lift on it that makes it 10 1/2 feet tall, so the dealers won't even look at it because they can't get it in their garage and they won't work on it outside. The nearest dealer that can get it inside is 80 miles away.

At any rate, I will try to source one of these TechIIs. I got the P-code of Password not correct with my SnapOn Scanner.

Thanks for the help and if you come up with anything else lemme know, thanks

ES
 
  #5  
Old 02-10-03, 05:50 PM
fishpounder's Avatar
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Location: Iowa
Posts: 58
Attempt to start and let die.

Leave key in run position for 10 minutes or so until security light goes out.

Vehicle should now start.

May have to repeat a few times to aquire passcode.
 
  #6  
Old 02-10-03, 09:12 PM
otter_
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Vehicle has passlock not passkey. The difference is that passlock uses a hall-effect sensing system in the ignition lock to verify that a properly cut key is being used to turn the ignition cylinder. No code is required. All that is needed is for the key to turn past two sensors, thus breaking a magnetic field.

I would be looking at the ignition lock or wiring related to passlock.

I can't offer anything more than the above.
 
  #7  
Old 02-11-03, 03:27 AM
Joe_F
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Me personally, I'd start with all the TSB's on the ignition related problems first, that's the best place to start
 
  #8  
Old 02-11-03, 03:54 PM
ny25621
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Hi guys,

Thanks for all the help. I got a new lock cylinder, and a new key coded to the original key code. I compared it to the old keys, and even though they are the same code, and both keys will operate the lock cylinder, the new key "looks" significantly different as far as the hills and valleys in it are concerned. Installed the new part, the lock cylinder only. The dealer said the case may need replacing as well (that houses the hall effect sensors) so hopefully this is only a magnetic problem.

On another note....This IS intermittent...It only does the security light and no start if left outdoors and it is extremely cold...If vehicle is left in warm garage it works flawlessly.

Thanks again for the help.

ES
 
  #9  
Old 02-13-03, 02:28 PM
ny25621
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Hey all,

It's still flashing the Security light when left outside in the cold. Like Joe said, I can't throw parts at it anymore, costs too much $$$. Have been instructed to ship it off to the dealer since they can get more codes with the TechII than I can with my Snap-On scanner.

Thanx anyway for the help

ES
Fleet Tech
 
  #10  
Old 02-13-03, 04:14 PM
Joe_F
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Ummm, no that's not the answer . The scanner probably has little to do with it.

Again, you should investigate the bulletins that pertain to the security system as I indicated in an earlier reply. This will likely lead you to the problem.

I would assume as a fleet company, you have Alldata. In such case, you should be able to find the needed bulletins that pertain to this system. They should steer you in the right direction.

The dealer shouldn't have to be your answer
 
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