AutoCodes – Subaru – C0109 Subaru

C0109 Subaru Code - Power Supply Voltage Failure

Quick Answer

The Anti-Lock Brake System (ABS) Module monitors the Power Supply Voltage. Common causes include Faulty Anti-Lock Brake System (ABS) Module, Anti-Lock Brake System (ABS) Module harness is open or shorted, Anti-Lock Brake System (ABS) Module 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
C0109 Subaru indicates Power Supply Voltage Failure.
Common causes
Common causes include Faulty Anti-Lock Brake System (ABS) Module, Anti-Lock Brake System (ABS) Module harness is open or shorted, Anti-Lock Brake System (ABS) Module 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.
AI answers can be wrong. Verify repairs with testing. Open full chat
Code Popularity 13,358
How popular is this code, among other codes? Low
Table of contents Created and updated by William Orellana on May 05, 2020
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Code C0109 Subaru Description

The Anti-Lock Brake System (ABS) Module monitors the Power Supply Voltage. The ABS Module sets the OBDII code when the Power Supply Voltage is not to factory specifications.
OBDII Code C0109 Subaru - Power Supply Voltage Failure - AutoCodes.com
C0109 Subaru Code - Power Supply Voltage Failure

What are the Possible Causes of the DTC C0109 Subaru?

  • Faulty Anti-Lock Brake System (ABS) Module
  • Anti-Lock Brake System (ABS) Module harness is open or shorted
  • Anti-Lock Brake System (ABS) Module circuit poor electrical connection

How to Fix the DTC C0109 Subaru?

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 C0109 Subaru 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 C0109 Subaru Code

1. What are the common symptoms of OBDII code C0109 Subaru (Power Supply Voltage Failure)?

- Common symptoms include illuminated dashboard warning lights, loss of power steering assistance, and potential issues with the vehicle's electrical systems.

2. What are the possible causes of OBDII code C0109 in a Subaru?

- The code C0109 typically indicates a power supply voltage failure, which can be caused by a faulty power steering control module, damaged wiring, or a weak battery.

3. How can I diagnose OBDII code C0109 in my Subaru?

- To diagnose code C0109, a diagnostic scan tool is typically used to retrieve the fault codes from the vehicle's computer system. A thorough inspection of the power steering control module and related wiring is also recommended.

4. Can I still drive my Subaru with OBDII code C0109 present?

- While it may be possible to drive your Subaru with code C0109 present, it is not recommended as it can lead to potential safety hazards and further damage to the vehicle's electrical system.

5. How can I repair OBDII code C0109 in my Subaru?

- Repairing code C0109 may involve replacing the power steering control module, repairing damaged wiring, or addressing any underlying battery issues. It is recommended to consult a professional mechanic for an accurate diagnosis and proper repair.

6. Is it safe to reset the OBDII code C0109 without fixing the underlying issue?

- Resetting the OBDII code without addressing the underlying issue may temporarily clear the warning light, but the problem will likely reoccur. It is important to diagnose and repair the root cause of the code to ensure safe and reliable operation of the vehicle.

7. Can a weak battery cause OBDII code C0109 in a Subaru?

- Yes, a weak or failing battery can potentially cause power supply voltage failure, resulting in OBDII code C0109 in a Subaru. It is recommended to have the battery tested and replaced if necessary.

8. How much does it typically cost to repair OBDII code C0109 in a Subaru?

- The cost of repairing OBDII code C0109 in a Subaru can vary depending on the underlying cause of the issue and the specific repairs needed. It is advisable to obtain a diagnosis from a qualified mechanic to determine the exact cost.

9. Can extreme weather conditions contribute to OBDII code C0109 in a Subaru?

- Extreme weather conditions, such as extreme cold or heat, can potentially affect the performance of the power steering control module and other electrical components, leading to power supply voltage failure and triggering OBDII code C0109.

10. Is it possible to prevent OBDII code C0109 in a Subaru through regular maintenance?

- Regular maintenance, including checking the battery health, inspecting wiring connections, and addressing any power steering system issues promptly, can help prevent power supply voltage failure and reduce the likelihood of OBDII code C0109 occurring.

1. What are the common symptoms of OBDII code C0109 in a Subaru related to power supply voltage failure?

The common symptoms include issues with starting the vehicle, dimming or flickering lights, and electrical system malfunctions.

2. What are the possible causes of OBDII code C0109 in a Subaru indicating power supply voltage failure?

Possible causes include a faulty alternator, damaged battery, loose or corroded electrical connections, or a malfunctioning voltage regulator.

3. How can I diagnose the OBDII code C0109 in my Subaru related to power supply voltage failure?

Diagnosing the code involves checking the battery voltage, inspecting the alternator, testing the voltage regulator, and examining the electrical connections for any damage or corrosion.

4. What are some repair tips for addressing OBDII code C0109 indicating power supply voltage failure in a Subaru?

Repair tips include replacing a faulty alternator or battery, repairing or replacing damaged electrical connections, cleaning corrosion off terminals, and ensuring proper grounding.

5. Can OBDII code C0109 in a Subaru be cleared/reset, or does it require immediate attention?

The code can be cleared/reset, but it is important to address the underlying power supply voltage issue to prevent further electrical system problems.

6. Is it safe to continue driving my Subaru with OBDII code C0109 related to power supply voltage failure?

It is not recommended to drive the vehicle extensively with this code as it can lead to further electrical system damage and potential breakdowns.

7. How much does it typically cost to repair OBDII code C0109 in a Subaru indicating power supply voltage failure?

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

8. Are there any preventive maintenance steps I can take to avoid OBDII code C0109 in my Subaru?

Regularly checking the battery, alternator, and electrical connections for signs of wear or damage, and ensuring timely replacements can help prevent power supply voltage failures.

9. Can extreme weather conditions or driving habits contribute to triggering OBDII code C0109 in a Subaru?

Yes, extreme temperatures, frequent short trips, or heavy electrical loads can strain the charging system and contribute to power supply voltage failures triggering the code.

10. How long does it typically take to repair OBDII code C0109 related to power supply voltage failure in a Subaru?

The repair time can vary based on the specific issue, but it may take anywhere from a couple of hours to a full day for diagnosis and repair.

2. What are the possible causes of OBDII code C0109 Subaru?

Possible causes include a faulty power supply unit, poor electrical connections, damaged wiring harnesses, or issues with the vehicle's battery or alternator.

3. How can I diagnose OBDII code C0109 Subaru?

Diagnosis typically involves using a diagnostic scanner to retrieve the trouble code, inspecting the power supply unit and related components for damage, and testing the electrical connections for proper voltage.

4. Can I drive my Subaru with OBDII code C0109 (Power Supply Voltage Failure)?

It is generally not recommended to drive the vehicle with this code present, as it can lead to electrical issues that may affect the vehicle's performance and safety.

5. How can I repair OBDII code C0109 Subaru?

Repair methods may include replacing the faulty power supply unit, repairing damaged wiring or electrical connections, and ensuring proper voltage output from the battery and alternator.

6. What are some tips for preventing OBDII code C0109 from recurring?

Regularly inspecting the vehicle's electrical system, maintaining the battery and alternator, and addressing any electrical issues promptly can help prevent the code from recurring.

7. Can a DIY enthusiast fix OBDII code C0109 Subaru?

While some basic diagnostic and repair tasks can be performed by DIY enthusiasts, addressing complex electrical issues may require professional assistance to ensure proper diagnosis and repair.

8. Is OBDII code C0109 Subaru a serious issue?

While the code itself may not pose an immediate threat to vehicle safety, ignoring it can lead to potential electrical problems that may impact the vehicle's performance and reliability.

9. How long does it typically take to repair OBDII code C0109 Subaru?

The repair time can vary depending on the specific cause of the code and the extent of the repairs needed. It is advisable to consult a professional technician for an accurate estimate.

10. Can OBDII code C0109 Subaru be reset without fixing the underlying issue?

Resetting the code without addressing the underlying cause will only temporarily clear the check engine light. The code is likely to reappear if the root issue is not resolved.

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