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 MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 647 (THEFT DETERRENT SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC B2721: INVALID PASS-KEY® DETECTIONTEST DESCRIPTION
1999 GMC Forward Control 5.7 R, Automatic
Test Description
1999 GMC Forward Control 5.7 R, AutomaticSECTION Test Description
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers on the diagnostic table.
- Tests for other PASS-Key® DTCs stored in the BCM that will cause a DTC B2721 to set. These DTCs must be diagnosed first.
- Tests for an intermittent or incorrect PASS-Key® Resister reading due to an incorrect or malfunctioning ignition key.
RENDER: 1.0x
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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.