AutoCodes – Buick – B2721 Buick

B2721 Buick 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 Buick 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 971

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 Buick 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 Buick - PASS-Key Detection Circuit - AutoCodes.com — B2721 Buick Code - PASS-Key Detection Circuit

What does this mean?

What are the Possible Causes of the DTC B2721 Buick?

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

How to Fix the DTC B2721 Buick?

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 Buick 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 Buick Code

1. What are the common symptoms of OBDII code B2721 in a Buick related to the PASS-Key detection circuit?

- Common symptoms include issues with starting the vehicle, intermittent or persistent no-start conditions, and the security light staying illuminated on the dashboard.

2. What could be the possible causes of OBDII code B2721 in a Buick related to the PASS-Key detection circuit?

- Possible causes may include a faulty ignition lock cylinder, damaged or faulty PASS-Key sensor, wiring issues in the PASS-Key system, or a malfunctioning Body Control Module (BCM).

3. How can I diagnose OBDII code B2721 in my Buick related to the PASS-Key detection circuit?

- Diagnosis involves checking the PASS-Key system components for any visible damage, testing the PASS-Key sensor, inspecting the wiring for continuity and shorts, and using a diagnostic scan tool to retrieve specific trouble codes.

4. Is it safe to continue driving my Buick with OBDII code B2721 related to the PASS-Key detection circuit?

- It is not recommended to drive the vehicle with this code present, as it can lead to potential starting issues and security system malfunctions that may leave you stranded.

5. Can I repair OBDII code B2721 in my Buick related to the PASS-Key detection circuit myself?

- While some DIY enthusiasts may attempt to troubleshoot and repair this issue, it is recommended to seek professional help from a certified mechanic or dealership due to the complexity of the PASS-Key system.

6. Are there any quick tips for resolving OBDII code B2721 in a Buick related to the PASS-Key detection circuit?

- Quick tips include checking for blown fuses related to the PASS-Key system, ensuring the key is in good condition and properly programmed, and inspecting the wiring harness for any visible damage.

7. How much does it typically cost to repair OBDII code B2721 related to the PASS-Key detection circuit in a Buick?

- Repair costs can vary depending on the exact cause of the issue, but they may range from $100 to $500 or more, including parts and labor.

8. Will resetting the OBDII code B2721 related to the PASS-Key detection circuit make it go away permanently?

- Resetting the code may temporarily clear the error, but if the underlying issue is not addressed, the code is likely to reappear once the problem resurfaces.

9. Can extreme weather conditions affect the triggering of OBDII code B2721 in a Buick related to the PASS-Key detection circuit?

- Yes, extreme cold or heat can sometimes exacerbate existing issues with the PASS-Key system components, leading to the triggering of this code.

10. How long does it typically take to repair OBDII code B2721 related to the PASS-Key detection circuit in a Buick?

- The repair time can vary depending on the exact cause of the issue and the expertise of the technician, but it may take a few hours to a full day to complete the repair process.