AutoCodes – Generic – P0379

P0379 Code - Timing Reference High Resolution Signal 'B' No Pulses

Quick Answer

The optical sensor provides a high resolution signal to the Powertrain Control Module (PCM) by counting pulses on the sensor disk located in the injection pump. Common causes include Timing Reference Optical Sensor harness is open or shorted, Timing Reference Optical Sensor circuit poor electrical connection, Faulty Timing Reference Optical Sensor. 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: P0379 indicates Timing Reference High Resolution Signal 'B' No Pulses.
Common causes: Common causes include Timing Reference Optical Sensor harness is open or shorted, Timing Reference Optical Sensor circuit poor electrical connection, Faulty Timing Reference Optical Sensor.
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 6,873

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 Jun 14, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0379 Description

The optical sensor provides a high resolution signal to the Powertrain Control Module (PCM) by counting pulses on the sensor disk located in the injection pump. The high resolution is one of the most important inputs by the PCM for fuel control and timing. This test monitors the number of high resolution pulses which have been missed (not detected). It's based on a comparison between the number of pulses that were detected since the last pump cam pulse and the number of the pulses that should have occurred. There are approximately 64 high resolution pulses for every cam pulse.

OBDII Code P0379 - Timing Reference High Resolution Signal 'B' No Pulses - AutoCodes.com — P0379 Code - Timing Reference High Resolution Signal 'B' No Pulses

What does this mean?

What are the Possible Causes of the DTC P0379?

Timing Reference Optical Sensor harness is open or shorted
Timing Reference Optical Sensor circuit poor electrical connection
Faulty Timing Reference Optical Sensor
Damaged Powertrain Control Module (PCM)

How to Fix the DTC P0379?

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 P0379 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 P0379 code?

Need more information on how to fix the P0379 code? Get Access to Factory Service Manuals

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Information for Specific Makes

P0379 Mercedes-Benz — Timing Reference High Resolution Signal 'B' No Pulses

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.