AutoCodes – Chevrolet – B2721 Chevrolet

B2721 Chevrolet Code - PASS-Key Detection Circuit

Quick Answer

The Body Control Module (BCM) supplies a 5 volt signal and a ground circuit for the PASS-KeyÂ® system. Common causes include Faulty Ignition Key, Faulty Ignition Lock Cylinder, Faulty Body Control Module (BCM). Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: B2721 Chevrolet indicates PASS-Key Detection Circuit.
Common causes: Common causes include Faulty Ignition Key, Faulty Ignition Lock Cylinder, Faulty Body Control Module (BCM).
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 1,566

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jan 26, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B2721 Chevrolet Description

The Body Control Module (BCM) supplies a 5 volt signal and a ground circuit for the PASS-KeyÂ® system. This allows the BCM to detect PASS-KeyÂ® resistance values. Inserting the PASS-KeyÂ® (with resistor pellet) in the ignition lock cylinder completes the PASS-KeyÂ® circuit. Contacts in the ignition lock cylinder mate with the pellet contacts. The BCM compares the resistance value of the key pellet to the valid resistance programmed into the BCM. If the proper resistance value is read, the BCM allows the following functions to occur: The theft deterrent relay to energize, The steering column to unlock and The BCM sends a message through the serial data line to the Powertrain Control Module (PCM) to enable fuel delivery. If the resistance value is incorrect, a malfunction is present and a DTC will set.

OBDII Code B2721 Chevrolet - PASS-Key Detection Circuit - AutoCodes.com — B2721 Chevrolet Code - PASS-Key Detection Circuit

What does this mean?

What are the Possible Causes of the DTC B2721 Chevrolet?

Faulty Ignition Key
Faulty Ignition Lock Cylinder
Faulty Body Control Module (BCM)

How to Fix the DTC B2721 Chevrolet?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B2721 Chevrolet code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about B2721 Chevrolet Code

1. What does the OBDII code B2721 mean for a Chevrolet?

Code B2721 indicates an issue with the PASS-Key detection circuit, which is part of the vehicle's anti-theft system responsible for verifying the proper key is being used.

2. What are the common symptoms of code B2721 in a Chevrolet?

Common symptoms include the engine not starting, the security light illuminating on the dashboard, and potential intermittent starting issues.

3. What causes the B2721 code to appear on a Chevrolet?

This code is typically caused by a faulty ignition key, a damaged ignition lock cylinder, corroded or loose wiring, or a malfunctioning PASS-Key module.

4. Can I drive my Chevrolet with a B2721 code?

Driving may be possible if the engine starts, but the vehicle could unexpectedly fail to start later. Itâ€™s best to address the issue promptly to avoid being stranded.

5. How do I diagnose the B2721 code in a Chevrolet?

Diagnosing involves checking the key and ignition cylinder for wear or damage, inspecting wiring and connectors for corrosion or breaks, and using a scan tool to monitor the PASS-Key system.

6. How can I fix the B2721 code on my Chevrolet?

Repairs may include replacing a worn ignition key, repairing damaged wiring, cleaning corroded connections, or replacing the ignition lock cylinder or PASS-Key module.

7. Can a weak battery cause the B2721 code in a Chevrolet?

A weak or failing battery can sometimes cause issues with the PASS-Key system, as it may not provide adequate voltage for proper module operation.

8. How much does it cost to repair the B2721 code on a Chevrolet?

Repair costs vary depending on the issue but generally range from $100 to $500, with key or ignition cylinder replacement being on the lower end and module repairs on the higher end.

9. Does the B2721 code require reprogramming the key or module?

In some cases, replacing the ignition key or PASS-Key module may require reprogramming to ensure proper communication with the vehicle's security system.

10. Can a locksmith fix the B2721 code on my Chevrolet?

Yes, a qualified automotive locksmith can often address issues related to worn keys or ignition lock cylinders and may also assist with reprogramming if needed.