P0343 SATURN - Camshaft Position Sensor Circuit High Voltage
- Camshaft Position Sensor harness is open or shorted
- Camshaft Position Sensor circuit poor electrical connection
- Faulty starter motor
- Starting system circuit
- Dead (Weak) battery
- Lack/Loss of Power
- Engine Stall
The Camshaft Position (CMP) Sensor sensor works in conjunction with a 1X reluctor wheel on the camshaft. The Powertrain Control Module (PCM) provides a 12 volt power supply to the CMP sensor as well as a ground and a signal circuit.
The CMP sensor determines whether a cylinder is on a firing stroke or on an exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads. The PCM uses this 1X signal in combination with the Crankshaft Position sensor 24X signal in order to determine crankshaft position and stroke. This diagnostic for the Camshaft Position sensor tests for a loss of Camshaft Position sensor signal.
Observe that as long as the Crankshaft Position sensor 24X signal is available, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM incorrectly synchronized to the exhaust stroke and will re-sync to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.