AutoCodes – Mercedes-Benz – P0381 Mercedes-Benz

P0381 Mercedes-Benz Code - Glow Plug/Heater Indicator Circuit Malfunction

Quick Answer

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. Common causes include Faulty Glow Plug, Glow Plug harness is open or shorted, Glow Plug 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: P0381 Mercedes-Benz indicates Glow Plug/Heater Indicator Circuit Malfunction.
Common causes: Common causes include Faulty Glow Plug, Glow Plug harness is open or shorted, Glow Plug 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 5,516

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Apr 16, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0381 Mercedes-Benz Description

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The Engine Control Module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage. The California Glow Plug system has eight individual glow plug supply circuits between the controller and the glow plugs. If the feedback voltage from the controller to the ECM is not within range, DTC P0380 will set.

OBDII Code P0381 Mercedes-Benz - Glow Plug/Heater Indicator Circuit Malfunction - AutoCodes.com — P0381 Mercedes-Benz Code - Glow Plug/Heater Indicator Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC P0381 Mercedes-Benz?

Faulty Glow Plug
Glow Plug harness is open or shorted
Glow Plug circuit poor electrical connection

How to Fix the DTC P0381 Mercedes-Benz?

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 P0381 Mercedes-Benz 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.

Need more information about the P0381 Mercedes-Benz code?

Need more information on how to fix the P0381 Mercedes-Benz code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0381 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area

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 P0381 Mercedes-Benz Code

1. What are common symptoms of OBDII code P0381 in a Mercedes-Benz related to the glow plug/heater indicator circuit malfunction?

- Common symptoms include hard starting, rough idling, reduced engine performance, and the glow plug indicator light staying illuminated.

2. What are the possible causes of OBDII code P0381 in a Mercedes-Benz?

- The code P0381 can be triggered by issues such as a faulty glow plug, defective glow plug relay, damaged wiring or connectors, or a malfunctioning ECM.

3. How can I diagnose the cause of OBDII code P0381 in my Mercedes-Benz?

- To diagnose the issue, you can perform a visual inspection of the glow plug system, check the resistance of individual glow plugs, test the glow plug relay, and inspect the wiring harness for damage.

4. Can driving with OBDII code P0381 in a Mercedes-Benz cause further damage to the vehicle?

- Continuously driving with a glow plug/heater indicator circuit malfunction can lead to poor engine performance, decreased fuel efficiency, and potential damage to the engine over time.

5. Is it safe to continue driving my Mercedes-Benz with OBDII code P0381 until I can repair it?

- While the vehicle may still operate with this code present, it is not recommended to delay repairs as it can lead to more severe issues and higher repair costs in the long run.

6. How much does it typically cost to repair OBDII code P0381 in a Mercedes-Benz?

- The cost to repair OBDII code P0381 can vary depending on the specific cause of the issue, but it may range from $200 to $500 for parts and labor.

7. Can I clear the OBDII code P0381 in my Mercedes-Benz with a simple reset or disconnecting the battery?

- Clearing the fault code temporarily by resetting the system or disconnecting the battery may not solve the underlying issue causing code P0381. It's best to diagnose and repair the root cause.

8. Are there any DIY tips for troubleshooting OBDII code P0381 in a Mercedes-Benz?

- DIY tips include checking the glow plugs visually, testing the glow plug relay with a multimeter, inspecting the wiring connections, and ensuring proper ECM communication.

9. How long does it take to repair OBDII code P0381 in a Mercedes-Benz at a professional repair shop?

- The repair time for OBDII code P0381 can vary depending on the exact cause, but it typically takes 1-2 hours for diagnosis and repair at a professional repair shop.

10. Will fixing OBDII code P0381 improve the overall performance and fuel efficiency of my Mercedes-Benz?

- Yes, repairing code P0381 will restore proper glow plug operation, improving engine starting performance, idling smoothness, fuel efficiency, and overall engine health.