P0343

CIRCUIT DESCRIPTION
The camshaft position (CMP) sensor works in conjunction with a 1X reluctor wheel on the camshaft. The powertrain control module (PCM) provides a 12-volt reference, a low reference, and a signal circuit to the CMP sensor.

The CMP sensor determines whether a cylinder is on a tiring stroke or on an exhaust stroke. A magnet within the sensor produces a magnetic field. The reluctor wheel of the rotating camshaft interrupts this magnetic field. The sensor's internal circuitry detects this field, and produces a signal which the PCM reads. The PCM uses this 1X signal in combination with the 24X signal of the crankshaft position (CKP) sensor. The PCM uses this information in order to determine the crankshaft position and the stroke. The PCM monitors for a loss of the CMP sensor signal.

As long as the PCM receives the CKP sensor 24X signal, the engine will start. The PCM can determine the top dead center for all of the cylinders just by using the CKP sensor 24X signal. The PCM uses the CMP sensor 1X signal in order to determine which stroke the cylinder at the top dead center is on. The PCM determines if the cylinder is on the firing stroke or on the exhaust stroke. The system attempts synchronization, and looks for an increase in the engine speed, indicating that the engine started. If the PCM does not detect an increase in the engine speed, the PCM assumes the PCM is incorrectly synchronized to the exhaust stroke. The PCM synchronizes to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.

CONDITIONS FOR RUNNING THE DTC
The engine speed is less than 4000 RPM.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
^ The following conditions may cause this DTC to set:
- Camshaft reluctor wheel damage
- A sensor that is in contact with the reluctor wheel
^ For an intermittent conditions, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-8:

Steps 9-21:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the fault is present.
4. If the duty cycle is present at the PCM connector, the 12-volt reference circuit, and the low reference circuit of the CMP sensor are OK.
5. This step tests the 12-volt reference circuit of the CMP sensor.
6. This step tests the low reference circuit of the CMP sensor.
9. This step tests for a short to voltage on the CMP sensor signal circuit.
10. This step tests for a short to ground on the CMP sensor signal circuit.