What does it mean?
A stored code P0386 means that the powertrain control module (PCM) has detected a problem with the crankshaft position sensor (CPS) or circuit. Sensor B is indicative of the secondary CPS in a system that may utilize multiple crankshaft position sensors for various functions. The PCM uses input signals from the CPS and the camshaft sensor/s to monitor the position and revolutions per minute (RPM) of the engine, manage fluctuations in ignition timing, and calculate fuel delivery strategy.
Variations in engine configuration will dictate the number of camshaft sensors that are used in conjunction with a single CPS. Each camshaft sensor has a circuit (or circuits) dedicated to providing the PCM with individual input signal/s. Since the crankshaft turns at twice the speed of the camshaft/s, it is critical that the PCM is able to distinguish between engine intake and exhaust stokes.
Crankshaft position and speed are compared to the speed and position of the camshaft/s in order to prevent engine damage. The most common CPS design utilizes an electromagnetic hall-effect sensor positioned in very close proximity (usually only several thousandths of an inch) to the crankshaft to form a circuit completing engine ground. In most cases, a reluctor ring (with precisely machined teeth) affixed to the crankshaft or crankshaft pulley, provides this engine ground.
In other cases, cogs meticulously integrated into the crankshaft itself, provide the engine ground. The CPS is positioned so that these teeth/cogs pass very closely to its magnetic end. As the crankshaft rotates, the raised areas pass by the sensor and complete the electromagnetic circuit. When the indentations (between the teeth) pass the CPS, the circuit is briefly interrupted.
Since the camshaft rotates very quickly, the process of repeatedly completing and interrupting the circuit occurs in milliseconds. This progression of completing and interrupting the CPS circuit produces a waveform pattern. This pattern is recognized by the PCM as crankshaft position. The CPS and all of the camshaft position sensors function in much the same manner. When the engine is running, the PCM constantly compares input signals from the crankshaft and the camshafts.
If the crankshaft position is not within a specified degree of variation from the camshaft/s, under a given set of circumstances for a set period of time, a P0386 code will be stored and a malfunction indicator lamp may be illuminated. Typically, when this code is set, the engine will not start. If the engine does start, it will likely run very poorly.