OBD-II code P0379 indicates that the powertrain control module (PCM) has detected no pulses from the 'B' high-resolution timing reference signal. This signal is typically generated by a camshaft or crankshaft position sensor and is critical for precise ignition and fuel injection timing. The fault may prevent the engine from starting or cause severe running issues.
The sensor itself is the most common failure point, often due to internal electrical breakdown, heat damage, or contamination.
Wiring between the sensor and PCM can become chafed, broken, or corroded, interrupting the signal.
Poor contact at the connector due to moisture ingress, bent pins, or vibration can cause an intermittent or complete loss of signal.
The toothed wheel on the camshaft or crankshaft may have broken teeth, debris, or excessive runout, preventing the sensor from generating pulses.
A stretched chain or slipped belt can alter the relationship between the crankshaft and camshaft, leading to a perceived loss of signal.
An internal fault in the PCM is possible but should only be considered after all other causes have been thoroughly ruled out.
The 'B' signal typically designates a specific high-resolution timing input, often from a camshaft position sensor or a secondary crankshaft sensor. The exact sensor varies by vehicle make and model.
It is not recommended. The engine may stall unexpectedly or fail to start, and continued driving can cause catalytic converter damage due to misfires.
No. In the vast majority of cases, the problem is a faulty sensor, wiring issue, or mechanical fault. Replacing the PCM without a thorough diagnosis is usually a misdiagnosis and a waste of money.
P0378 indicates an intermittent or erratic signal (pulses present but irregular), while P0379 means no pulses are detected at all from the 'B' signal circuit.