AutoCodes – GMC – B3779 GMC

B3779 GMC Code - Air Flow Control 9

Quick Answer

The Heating, Ventilation, and Air Conditioning (HVAC) control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Common causes include Faulty Mode Actuator, Mode Actuator harness is open or shorted, Mode Actuator circuit poor electrical connection. 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: B3779 GMC indicates Air Flow Control 9.
Common causes: Common causes include Faulty Mode Actuator, Mode Actuator harness is open or shorted, Mode Actuator circuit poor electrical connection.
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 15,780

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 Mar 16, 2020

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B3779 GMC Description

The Heating, Ventilation, and Air Conditioning (HVAC) control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 5-volt reference source voltage to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The control circuit uses either a 0, 2.5 or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions.

OBDII Code B3779 GMC - Air Flow Control 9 - AutoCodes.com — B3779 GMC Code - Air Flow Control 9

What does this mean?

What are the Possible Causes of the DTC B3779 GMC?

Faulty Mode Actuator
Mode Actuator harness is open or shorted
Mode Actuator circuit poor electrical connection
Faulty Heating and Cooling Systems (HVAC) Control Module

How to Fix the DTC B3779 GMC?

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 does this mean?

Code Tech Notes

B3779 02 Air Flow Control 9 Feedback Circuit Short to Ground
B3779 05 Air Flow Control 9 Feedback Circuit Short to Battery or Open
B3779 61 Air Flow Control 9 Circuit Actuator Stuck

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B3779 GMC 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 B3779 GMC Code

1. What are common symptoms of OBDII code B3779 GMC?

The common symptoms of OBDII code B3779 GMC, titled Air Flow Control 9, include poor engine performance, rough idling, and decreased fuel efficiency.

2. What are the possible causes of OBDII code B3779 GMC?

Possible causes of OBDII code B3779 GMC can include a faulty air flow control sensor, issues with the air intake system, or a problem with the engine control module.

3. How can I diagnose OBDII code B3779 GMC?

Diagnosing OBDII code B3779 GMC typically involves using an OBDII scanner to retrieve the code, conducting visual inspections of the air flow control system, and testing the relevant sensors.

4. Can a dirty air filter trigger OBDII code B3779 GMC?

Yes, a dirty air filter can restrict airflow to the engine, causing issues with air flow control and potentially triggering OBDII code B3779 GMC.

5. Are there any simple repair tips for OBDII code B3779 GMC?

Simple repair tips for OBDII code B3779 GMC may include cleaning or replacing the air flow control sensor, checking and cleaning the air intake system components, and ensuring proper connection of electrical connectors.

6. Is it safe to continue driving with OBDII code B3779 GMC triggered?

It is not recommended to continue driving with OBDII code B3779 GMC triggered, as it can lead to further engine problems and potential damage if left unresolved.

7. How much does it typically cost to repair OBDII code B3779 GMC?

The cost to repair OBDII code B3779 GMC can vary depending on the specific cause of the issue, but it may range from a few hundred to over a thousand dollars, including parts and labor.

8. Can OBDII code B3779 GMC be triggered by a loose or damaged vacuum hose?

Yes, a loose or damaged vacuum hose in the air intake system can disrupt air flow control and potentially trigger OBDII code B3779 GMC.

9. Will resetting the OBDII system clear OBDII code B3779 GMC?

Resetting the OBDII system may temporarily clear OBDII code B3779 GMC, but if the underlying issue is not addressed, the code is likely to reappear after driving the vehicle for some time.