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Engine-Codes – Subaru – C0042 Subaru

C0042 Subaru Code - Power Supply Voltage Failure

Quick Answer

The C0042 diagnostic trouble code for Subaru vehicles indicates a power supply voltage failure. Common causes include Faulty alternator, Dead or dying battery, Loose or corroded battery terminals. 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
C0042 Subaru indicates Power Supply Voltage Failure.
Common causes
Common causes include Faulty alternator, Dead or dying battery, Loose or corroded battery terminals.
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.
What is this?
Table of contents Created and updated by William Orellana on Aug 18, 2024
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Code C0042 Subaru Description

The C0042 diagnostic trouble code for Subaru vehicles indicates a power supply voltage failure. This means that there is an issue with the electrical system supplying the necessary voltage to various components within the vehicle. The power supply voltage is crucial for the proper functioning of multiple systems, including the engine control module, transmission control module, ABS module, and other critical components. When the power supply voltage is not within the specified range, it can lead to erratic behavior in these systems, potentially causing performance issues and even safety concerns.

OBDII Code C0042 Subaru - Power Supply Voltage Failure
C0042 Subaru Code - Power Supply Voltage Failure

Common Causes of C0042 Subaru

  1. Faulty alternator
  2. Dead or dying battery
  3. Loose or corroded battery terminals
  4. Wiring harness issues
  5. Faulty power supply module

Symptoms of C0042 Subaru

  1. Check engine light illuminated on the dashboard
  2. Erratic behavior of electronic systems (e.g., lights flickering, radio cutting in and out)
  3. Engine stalling or rough idling
  4. Transmission shifting problems
  5. ABS or traction control warning lights activated

How to Fix C0042 Subaru

  1. Perform a thorough inspection of the battery, alternator, and wiring harness
  2. Test the alternator output and battery voltage
  3. Replace the alternator if it is faulty
  4. Clean or replace corroded battery terminals
  5. Check and repair any damaged wiring harness

Cost to Fix C0042 Subaru

The cost to repair a power supply voltage failure in a Subaru vehicle can vary depending on the specific cause of the issue. On average, the repair cost can range from $200 to $500, including parts and labor. However, as mentioned earlier, the actual repair costs can differ based on factors such as the location of the repair shop, the make and model of the vehicle, and the extent of the repairs needed. It's recommended to consult with a trusted mechanic or dealership for an accurate estimate tailored to your situation.

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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 C0042 Subaru Code

1. What are the common symptoms of OBDII code C0042 in a Subaru related to power supply voltage failure?

- Common symptoms include issues with power steering operation, ABS system malfunctions, and dashboard warning lights illuminating.

2. What are the possible causes of OBDII code C0042 in a Subaru indicating power supply voltage failure?

- The code C0042 in a Subaru may be triggered by a faulty ABS actuator, damaged wiring harness, or a malfunctioning electronic control unit (ECU).

3. How can I diagnose the OBDII code C0042 in my Subaru related to power supply voltage failure?

- Diagnosis involves using a scan tool to retrieve the code, inspecting the ABS system components, and testing the power supply voltage to identify the root cause.

4. Can a DIY enthusiast repair OBDII code C0042 in a Subaru caused by power supply voltage failure?

- Repairing this code typically requires specialized knowledge and tools, so it is recommended to seek professional help to resolve the issue effectively.

5. Are there any safety concerns associated with OBDII code C0042 in a Subaru due to power supply voltage failure?

- Yes, unresolved power supply voltage issues can affect the proper functioning of critical safety systems like ABS and power steering, potentially compromising vehicle safety.

6. Is it possible for other codes to be triggered along with OBDII code C0042 in a Subaru indicating power supply voltage failure?

- Yes, related codes such as ABS system fault codes or communication errors with other control modules may also be present when code C0042 is detected.

7. How long does it typically take to repair OBDII code C0042 in a Subaru caused by power supply voltage failure?

- The repair time can vary depending on the exact cause of the issue, but it may take a few hours to a day for a professional technician to diagnose and rectify the problem.

8. Can a weak car battery cause OBDII code C0042 in a Subaru related to power supply voltage failure?

- Yes, a weak or failing car battery can lead to voltage fluctuations that may trigger code C0042, so it's essential to ensure the battery is in good condition.

9. Are there any preventative measures to avoid encountering OBDII code C0042 in a Subaru due to power supply voltage failure?

- Maintaining a regular schedule of vehicle inspections and addressing any electrical issues promptly can help prevent power supply voltage failures that trigger code C0042.

10. Will driving with OBDII code C0042 in a Subaru caused by power supply voltage failure damage other vehicle components?

- Continuing to drive with this code present may lead to further damage to the ABS system components or electronic control unit, so it's best to address the issue promptly.

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