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 MANUALSCHEVROLET2001CAVALIER LS, 2.4 TREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 6 (ANTI-THEFT SYSTEM)DIAGNOSTIC TESTSDTC B2721: PASS-KEY(R) DETECTION CIRCUIT OUT OF RANGEDIAGNOSTIC PROCEDURE
2001 Chevrolet Cavalier LS, 2.4 T
Diagnostic Procedure
2001 Chevrolet Cavalier LS, 2.4 TSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2000 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
- Try each key provided with vehicle in ignition lock cylinder. Wait 3 minutes between each attempt to allow PASS-Key(R) timer sequence to reset. If one of the keys works, go to step 7 . If no keys work, go to next step.
- If ignition lock cylinder was recently replaced, see BCM/PASS-KEY(R) under PROGRAMMING. If ignition lock cylinder was not recently replaced, go to next step.
- Using scan tool, check for PASS-Key(R) DTCs B2722, B2723 or B2735. If any of these DTCs exist, perform appropriate diagnostic procedure. If none of these DTCs exist, go to next step.
- Using Interrogator Adapter Harness (J-35628-A), perform lock cylinder test, following Interrogator manufacturer's instructions. If problem is found, go to step 9 . If no problem is found, go to next step.
- Turn ignition off. Disconnect ignition lock cylinder connector C3. Turn ignition on. At BCM side of ignition lock cylinder connector C3, measure voltage between terminals "A" (Purple/White wire) and "B" (White/Black wire). If measurement is about 5 volts, go to next step. If measurement is not about 5 volts, go to step 8 .
- Turn ignition off. Reinstall all components and connectors. Turn ignition on. Clear DTCs. Wait 5 seconds and check for DTCs. If DTC B2721 is current, go to step 10 . If DTC B2721 is not current, system is operating properly.
- Replace malfunctioning ignition key. After repairs, go to step 11 .
- Check for intermittent malfunction in White/Black wire and Purple/White wire between BCM connector C1 and ignition switch connector C3. If no problem is found, go to next step. If problem is found, repair as necessary. After repairs, go to step 11 .
- Replace ignition lock cylinder. See REMOVAL & INSTALLATION in ANALOG INSTRUMENT PANELS - CORVETTE article. After repairs, go to step 11 .
- Replace BCM. See BODY CONTROL MODULE under REMOVAL & INSTALLATION. Program BCM. See BCM/PASS-KEY(R) under PROGRAMMING. After repairs, go to next step.
- Turn ignition off. Reinstall all components and connectors. Turn ignition on. Clear DTCs and recheck system operation.
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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.