What does it mean?
OBD II fault code P0379 is a generic code that is defined as “Timing reference, high resolution signal B -no pulses”, and is set when the PCM (Powertrain Control Module) detects no signals from an engine position sensor. Note that “signal/circuit B” in this definition refers to a problem in a part of the timing signal circuit, as opposed to a specific part or component.
In order for the PCM to regulate/control/determine engine speed, fuel delivery, ignition timing, and misfire diagnostic functions (among other functions), it 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 TDC (Top Dead Centre) position for that piston.
On many applications, this is done with a sensor that is mounted close to the harmonic balancer (aka crankshaft pulley), that is fitted with a reluctor ring whose teeth interrupt and complete a magnetic field by turns as the ring rotates with the crank shaft, thus creating the signal.
However, many applications also use sensors on the camshaft(s), injection pump, or flywheel/flex plate to either accomplish the same task, or to serve as a means to monitor the functioning of the crank shaft-mounted sensor. In addition, position sensors that are mounted on camshafts also serve to monitor and control variable valve/cam shaft timing.
Regardless of the sensor type or other design specifics, 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. The image below shows a typical engine position sensor, which in this case, is a Crankshaft Position Sensor. Note that while crankshaft position sensors often appear identical, all such sensors are unique to their application, and are therefore generally not interchangeable.