P0379 OBD Error Code: Problem & Solutions

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OBD II fault code P0379 is a generic code that is defined as “Timing reference, high resolution signal B -no pulses” and the "B" indicates the problem is with a portion of the system circuit, instead of a particular symptom or component. This diagnostic trouble code (DTC) is a generic powertrain code, which means it applies to OBD-II equipped vehicles which have an engine position sensor. P0379 is set when the PCM (Powertrain Control Module) detects no signals from an engine position sensor. PCM requires a timing reference signal to determine engine speed and position. This is accomplished by means of an engine position sensor, such as a crankshaft, camshaft or fuel pump position sensor.

OBD-II Code Decreased engine performance is technically defined as a Timing Reference High Resolution Signal "B" no Pulses. This code is detected when there are no high-resolution pulses from the optical sensor to the PCM. To regulate and determine engine speed, fuel delivery, ignition timing, and misfire diagnostic functions PCM relies on a series of signals from a sensor that measures the position of the #1 piston relative to a base setting that is in turn relative to the Top Dead Centre position for that piston. As soon as the PCM fails to detect a signal from the engine position sensor, it will set code P0379, and may also illuminate a warning light. Please note that the Check Engine Light is usually a symptom, but not all the time. With some vehicles, the PCM will actually wait until the problem is detected multiple times before this light is activated.

What causes this problem with the Timing Reference High Resolution Signal B No Pulses?

• Damaged or shorted wiring and connectors
• Defective Position Sensors
• Damaged or blocked reluctor wheels
• Adulterated Oil
• Faulty PCM

1. Powertrain Control Module - A powertrain control module, abbreviated PCM, is an automotive component, a control unit, used on motor vehicles. It is generally a combined control unit, consisting of the engine control unit (ECU) and the transmission control unit (TCU). Repair or replace the PCM if you discover it faulty
2. Optical Sensor - An optical sensor converts light rays into electronic signals. A perfect optical sensor is also crucial to avoid all related trouble codes.
3. Multimeter - A multimeter or a multitester, also known as a VOM (volt-ohm-milliammeter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance. It is a kind of diagnostic tool required to diagnose this error code.
4. Crankshaft Position Sensor - The crankshaft position sensor is a vital electronic device located in the engine of a car. Its purpose is to register the rate at which the crankshaft spins. This information is used by engine management systems to control the fuel injection or the ignition system timing and other engine parameters. Make sure it should work efficiently else replace it in no time.
5. Fuel Injection Control Module - The fuel injection control module (FICM) regulates fuel flow through the vehicle's injection pump and fuel injectors. For the smooth functioning of your vehicle make sure it should work smoothly as well. 

Keep in mind; problems don’t get better over time unless rectified. So, if you discover any of the below mentioned symptom in your vehicle then please take your vehicle to a reputed repair facility. Symptoms for this error code may include:

• Decreased engine performance
• Decreased fuel mileage
• Spark knock while acceleration
• Engine misfiring
• Check engine light Illumination

Repair of this issue is not as difficult as some others. However, this issue is also serious and need to be fixed as soon as possible. Repairs and replacements to fix this code may include:

• Repair damaged optical sensor circuit.
• Replace the faulty sensors.
• Repair or replace the damaged wiring and loose connections.
• Replace the faulty PCM which is very rare.

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Below are some basic steps to diagnose the trouble code P0379. However, we always recommend you to have it diagnose from an experienced technician because it may require some serious replacements and use of diagnostic tools.

• Record all codes present, as well as all available freeze frame data.
• Refer to the manual to identify and locate all engine position sensors, as well as all associated wiring.
• Determine the exact routing, function, and colour-coding of all relevant wiring to ensure that the correct circuits are tested later on.
• Once the correct sensor and circuit is identified, perform a thorough visual inspection of all wiring and connectors associated with that sensor.
• Look for damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors.
• Make repairs or replace wiring as required before clearing all codes and rescanning the system to see if the code returns.
• If no visible damage to wiring is found, refer to the manual to determine the recommended air gap between the tip of the sensor and the reluctor wheel.
• Perform a reference voltage tests on all relevant wiring, but be sure to disconnect the wiring from the PCM to avoid damaging the controller during this step.
• Check the resistance of the signal wire between the sensor and the PCM. Compare this value with the value stated in the manual, and make repairs or replace the wire if a deviation is found.
• If the fault persists but all electrical values agree with stated values, prepare to test the sensor itself.
• After performing all the above steps, if still the code persists then take your vehicle to repair facility for professional diagnosis and repair, since in some cases, this code can only be diagnosed accurately with the aid of an oscilloscope and a waveform library.

Common Mistakes When Diagnosing the P0379 Code

The most common mistake while diagnosing this error code is unnecessary or incorrect repairs/replacements. The quite often mistake noticed is replacement of crankshaft and camshaft sensor without checking them thoroughly wherein at the end the actual cause was something else.