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Engine-Codes – Generic – P138B

P138B Code - Glow Plug Module System Voltage

Quick Answer

The P138B diagnostic trouble code (DTC) refers to an issue with the Glow Plug Module System Voltage in a vehicle. Common causes include Faulty glow plug module, Wiring issues, such as a short circuit or open circuit, Malfunctioning engine control module (ECM). 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
P138B indicates Glow Plug Module System Voltage.
Common causes
Common causes include Faulty glow plug module, Wiring issues, such as a short circuit or open circuit, Malfunctioning engine control module (ECM).
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 Sep 09, 2024
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Code P138B Description

The P138B diagnostic trouble code (DTC) refers to an issue with the Glow Plug Module System Voltage in a vehicle. Glow plugs are a crucial component in diesel engines, as they help start the engine by heating the combustion chamber to facilitate ignition. The glow plug module controls the voltage supply to the glow plugs, ensuring they reach the necessary temperature for efficient starting. When the voltage supplied to the glow plug module falls outside the expected range, the P138B code is triggered.

OBDII Code P138B - Glow Plug Module System Voltage
P138B Code - Glow Plug Module System Voltage

Common Causes of P138B

  1. Faulty glow plug module.
  2. Wiring issues, such as a short circuit or open circuit.
  3. Malfunctioning engine control module (ECM).
  4. Poor electrical connections or corrosion.
  5. Battery or alternator problems affecting voltage supply.

Symptoms of P138B

  1. Difficulty starting the engine, especially in cold weather.
  2. Extended cranking times before the engine starts.
  3. Rough idling or misfiring.
  4. Decreased power and acceleration.
  5. Increased fuel consumption and emissions.

How to Fix P138B

  1. Diagnose the issue by using a scan tool to retrieve the DTC and inspect the glow plug module, wiring, and connections for any visible damage.
  2. Test the voltage supply to the glow plug module and verify if it falls within the specified range.
  3. Replace the faulty glow plug module if necessary and repair any damaged wiring or connections.
  4. Clear the DTC from the vehicle's memory and perform a test drive to ensure the issue has been resolved.
  5. If the problem persists, further diagnostics may be required to identify any underlying issues with the ECM or other electrical components.

Cost to Fix P138B

The cost of repairing the Glow Plug Module System Voltage issue can vary depending on the extent of the damage and the specific components that need replacement. In general, replacing a faulty glow plug module can range from $150 to $300, while addressing wiring or connection issues may add to the total repair cost. Labor rates at auto repair shops typically range from $80 to $150 per hour, with additional charges for diagnostic time and parts. It is advisable to consult with a qualified mechanic or service center to obtain an accurate estimate based on the make and model of the vehicle.

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Code P138B Information for Specific Makes

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 P138B Code

1. What are common symptoms of OBDII code P138B, Glow Plug Module System Voltage?

- Common symptoms include hard starting, rough idling, decreased fuel efficiency, and the illumination of the Check Engine Light.

2. What are the possible causes of OBDII code P138B?

- Possible causes include a faulty glow plug module, wiring issues, poor electrical connections, or a malfunctioning engine control module.

3. How can I diagnose the cause of OBDII code P138B?

- Diagnosis typically involves checking the glow plug module and related wiring for damage, testing electrical connections, and using a diagnostic scanner to read live data and pinpoint the issue.

4. Can I still drive my vehicle with OBDII code P138B present?

- It is not recommended to drive with this code present, as it can lead to performance issues and potential engine damage if left unresolved.

5. How can I repair OBDII code P138B, Glow Plug Module System Voltage?

- Repair involves replacing the faulty glow plug module, repairing any damaged wiring or connections, and clearing the code using a diagnostic scanner.

6. Are there any preventative maintenance tips to avoid OBDII code P138B?

- Regularly checking and maintaining the glow plug system, keeping electrical connections clean and secure, and addressing any warning signs promptly can help prevent this code from occurring.

7. Will resetting the Check Engine Light resolve OBDII code P138B?

- Resetting the Check Engine Light may temporarily turn it off, but if the underlying issue causing the code is not addressed, the light will likely come back on.

8. Is it safe to ignore OBDII code P138B if my vehicle is still running fine?

- Ignoring the code can lead to potential engine performance issues and decreased fuel efficiency over time, so it is best to address it promptly.

9. Can a DIY enthusiast fix OBDII code P138B at home?

- Depending on your mechanical skills and access to tools, replacing the glow plug module and addressing wiring issues can be done at home, but professional help may be needed for accurate diagnosis.

10. How much does it typically cost to repair OBDII code P138B at a repair shop?

- The cost of repairing this code can vary depending on the labor rates in your area, but it generally ranges from $200 to $500, including parts and labor.

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