P0323 indicates that the engine speed input signal to the powertrain control module (PCM) is intermittently dropping out or falling out of expected range. This signal is typically generated by a crankshaft position sensor or, on older distributor-equipped engines, by the magnetic pickup coil inside the distributor. Because the PCM loses track of engine speed momentarily, it can misfire spark or fuel pulses during those events.
Heat cycling, vibration, and oil contamination near the sensor harness are common. An intermittent open or high resistance in the signal or return wire is the single most frequent cause of P0323 and explains the 'intermittent' nature of the code.
Backed-out terminals, spread pins, or moisture intrusion in the connector can cause the signal to drop out only at certain engine positions or temperatures.
The internal magnetic or Hall-effect element can weaken and produce a signal that is occasionally too low in amplitude for the PCM to recognize reliably.
A chipped tooth, bent vane, or debris on the trigger surface creates periodic signal dropouts that look like an electrical intermittent to the PCM.
Worn distributor shaft, loose mounting, excessive play, or a bad distributor cap/rotor can cause erratic trigger readings even when the sensor itself is good.
Internal PCM failure is rare for this code and should only be considered after the sensor, wiring, ground, and trigger wheel have all been verified good.
Almost never. The code is set because the input signal is intermittent, and in the vast majority of cases the problem is the sensor itself, the wiring between the sensor and PCM, the connector, or the trigger wheel inside the engine or distributor. The PCM is a control module and is statistically the least likely cause; it should only be suspected after every input-side component has been ruled out by direct testing.
Short trips to a repair facility are usually possible, but the engine can stall without warning, which is a safety concern in traffic. If the engine dies at speed and power steering or brakes are affected, the vehicle should not be driven until the fault is corrected.
The fault only occurs when a connection briefly opens, when a sensor signal briefly drops below the PCM's recognition threshold, or when a damaged tooth passes the pickup. When conditions return to normal, the PCM clears the active fault and the code becomes stored/history until it reoccurs.
Not necessarily. On distributor engines, the pickup coil inside the distributor is often replaceable as a separate part, and many cases are resolved by repairing the external wiring or replacing just the pickup coil. A full distributor replacement is only warranted when the housing, shaft, or reluctor itself is mechanically worn.