PASS-Key Detection Circuit
What it means
B2721. PASS-Key Detection Circuit. This Chevy-enhanced code applies to Silverado, Sierra, Tahoe, Impala, Malibu.
Findings, check these first
- Worn ignition key pellet or dirty key contacts
- Faulty ignition lock cylinder PASS-Key contacts
- Damaged PASS-Key wiring inside the steering column
- Body control module (BCM) detection fault
- Aftermarket remote start bypass interfering with pellet reading
Standard procedure
- Try a spare key to rule out a worn pellet
- Inspect the lock cylinder contacts for wear and debris
- Measure key pellet resistance and compare to BCM learned value
- Check the column harness for chafing where it flexes with tilt
- Perform the GM security relearn procedure after any repair
Look up another code
Press / to jump to the box. Chevy-enhanced powertrain, body, chassis and network codes.
Sources and review
Review: checked against the recorded source material.
- B2721 Code PASS-Key Detection Circuit
archived reference page (autocodes.com via Wayback Machine)
Supports: code identity and Chevrolet application (page lists B2721 BUICK, CADILLAC, CHEVROLET and GMC variants)
Fetched generic page lists a B2721 CHEVROLET PASS-Key detection circuit variant, matching the catalog. Model and year fitment remain curator claims.
Last updated 2026-09-25.
Report a correction for B2721. Include your vehicle, the issue and a source if you have one.
This fault sits in the GM theft deterrent system. The GM security codes and Passlock relearn guide covers the families and the relearn cycles.