Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 2 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS - 5.3L)PROGRAMMINGTHEFT DETERRENT PASSWORD LEARN PROCEDURE10-MINUTE LEARN PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD
10-Minute Learn Procedure
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION 10-Minute Learn Procedure
WARNING: This page is about a different variant/trim than selected.
NOTE:
This procedure requires a Tech 2® scan tool and a Techline® terminal with current Service Programming System (SPS) software.
- Connect the Tech 2® to the vehicle.
- Select "REQUEST INFORMATION" under "SERVICE PROGRAMMING".
- Disconnect the Tech 2® from the vehicle and connect it to a Techline® terminal.
- On the Techline® terminal, select "THEFT MODULE RE-LEARN" under "SERVICE PROGRAMMING".
- Disconnect the Tech 2® from the Techline® terminal and connect it to the vehicle.
- Turn ON the ignition, with the engine OFF.
- Select "PROGRAM ECU" under "SERVICE PROGRAMMING".
- Attempt to start the engine, then release the key to ON (vehicle will not start).
- Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF (the vehicle is now ready to relearn the Passlock® Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK).
- Turn OFF the ignition, and wait 5 seconds.
- Start the engine (the vehicle has now learned the password).
- With the Tech 2®, clear any DTCs.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.