AutoCodes – GMC – C0309 GMC

C0309 GMC Code - Motor A/B Circuit High

Quick Answer

The transfer case motor is a bi-directional, permanent magnet, D.C. Common causes include Faulty Transfer Case Motor, Transfer Case Motor harness is open or shorted, Transfer Case Motor 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: C0309 GMC indicates Motor A/B Circuit High.
Common causes: Common causes include Faulty Transfer Case Motor, Transfer Case Motor harness is open or shorted, Transfer Case Motor 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 946

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 Jun 18, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code C0309 GMC Description

The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing Motor Control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, AUTO 4WD, 2H, N, and 4L ranges. While the transfer case motor is energized the transfer case shift control module also energizes the solenoid for the transfer case lock. The motor lock is disabled (locking action released) and free turning of the transfer case motor and sector shaft is then allowed.
This DTC detects a short to ground in Motor Control A or Motor Control B CKT.

OBDII Code C0309 GMC - Motor A/B Circuit High - AutoCodes.com — C0309 GMC Code - Motor A/B Circuit High

What does this mean?

What are the Possible Causes of the DTC C0309 GMC?

Faulty Transfer Case Motor
Transfer Case Motor harness is open or shorted
Transfer Case Motor circuit poor electrical connection

How to Fix the DTC C0309 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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the C0309 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 C0309 GMC Code

1. What are the common symptoms of OBDII code C0309 GMC (Motor A/B Circuit High)?

- Common symptoms include issues with the vehicle's traction control system, ABS system, and stability control system, such as warning lights on the dashboard and potential loss of stability control features.

2. What can cause the OBDII code C0309 GMC (Motor A/B Circuit High) to trigger?

- This code can be triggered by a malfunction in the motor A/B circuit high, which may be caused by damaged wiring, a faulty wheel speed sensor, or a problem with the ABS module.

3. How can I diagnose the OBDII code C0309 GMC (Motor A/B Circuit High)?

- Diagnosis typically involves using an OBDII scanner to retrieve the code, inspecting the wiring and connectors related to the motor A/B circuit, and testing the wheel speed sensors for proper functionality.

4. What are the possible repair options for OBDII code C0309 GMC (Motor A/B Circuit High)?

- Repair options may include repairing or replacing damaged wiring, replacing a faulty wheel speed sensor, or addressing any issues with the ABS module.

5. Can I continue driving my vehicle with the OBDII code C0309 GMC (Motor A/B Circuit High) present?

- While it may be possible to continue driving the vehicle, it is recommended to address the underlying issue promptly to prevent potential safety risks and further damage to the vehicle's systems.

6. How much does it typically cost to repair OBDII code C0309 GMC (Motor A/B Circuit High)?

- The cost of repair can vary depending on the specific cause of the issue, but it may involve expenses for parts and labor, with estimates ranging from a few hundred to a few thousand dollars.

7. Are there any DIY repair tips for addressing OBDII code C0309 GMC (Motor A/B Circuit High)?

- DIY enthusiasts with experience in automotive repair may attempt to diagnose and repair this issue by inspecting wiring, connectors, and sensors, but it is recommended to consult a professional if unsure.

8. Will resetting the OBDII code C0309 GMC (Motor A/B Circuit High) resolve the issue?

- Simply resetting the code may temporarily clear the warning lights, but if the underlying issue is not addressed, the code is likely to reappear once the problem is detected again.

9. How long does it take to repair OBDII code C0309 GMC (Motor A/B Circuit High)?

- The repair time can vary depending on the complexity of the issue and the availability of parts, but it may take anywhere from a few hours to a full day to complete the repair.

10. Can a mechanic help me with diagnosing and repairing OBDII code C0309 GMC (Motor A/B Circuit High)?

- Yes, a qualified mechanic or automotive technician can assist with diagnosing the issue using specialized equipment and perform the necessary repairs to resolve the OBDII code C0309 GMC (Motor A/B Circuit High).