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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4458
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Chevrolet Silverado 2500 HD How do you reset the security

Resolved Question:

How do you reset the security system on a 2004 Chevrolet deisel pickup?
Submitted: 5 years ago.
Category: Chevy
Expert:  Jerry Newton replied 5 years ago.
There is no "reset" procedure. I assume that your truck will not start, and you're getting a security light or message?
Customer: replied 5 years ago.
Yes--this happened before and I had the truck hauled to town and they reset it
Expert:  Jerry Newton replied 5 years ago.
What they did was probably "relearn" the security system, which is something you can do, but it's not a permanent fix. The Passlock system relies on a small voltage reading to enable starting, and wiring problems cause this small voltage to move slightly, to the point that the computer thinks the voltage is incorrect, and disables starting.

To relearn it yourself, here are the steps:

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

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

Keep in mind that if you have a wiring issue, this may not work, or it may work but the system will fail again at some point, until you have this accurately diagnosed and repaired.
Customer: replied 5 years ago.
I tried the procedure that you recomended and it did not work--the truck will not start.
Expert:  Jerry Newton replied 5 years ago.
If that does not work, then there is no work around..... that would defeat the purpose of a security system, no?

There are scan tool diagnostics for this, you'll need to retrieve the codes and diagnose it/have it diagnosed accordingly. The last shop that "reset" it didn't do you any favors, as they didn't address the root problem of a failing passlock sensor or loose wiring, and now you're stuck again. My advice is to have this diagnosed and repaired by the GM dealer, as they are intimately familiar with this system and where the problems lie, and how to diagnose them.
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