P0343

CIRCUIT DESCRIPTION
The camshaft position (CMP) sensor works in conjunction with a 1 X reluctor wheel on the camshaft. The powertrain control module (PCM) provides a 12-volt reference to the CMP sensor as well as a low reference 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 1 X signal in combination with the crankshaft position (CKP) sensor 24 X signal in order to determine CKP and stroke. This diagnostic for the CMP sensor checks for a loss of CMP sensor signal.

As long as the PCM receives the CKP sensor 24 X signal, the engine will start. The PCM can determine top dead center (TDC) for all cylinders by using the CKP sensor 24 X signal alone. The CMP sensor 1 X signal is used by the PCM to determine if the cylinder at TDC 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 assumes the PCM incorrectly synchronized to the exhaust stroke and re-syncs 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 4,000 RPM.

CONDITIONS FOR SETTING THE DTC
The PCM detects the CAM signal is stuck high when the signal should be low for 1.5 seconds.

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
^ The sensor coming in contact with the reluctor wheel

Using Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions such as RPM, load, vehicle speed, temperature, etc. that you observed. This will isolate when the DTC failed.

The CMP sensor output can be tested. The sensor must be supplied with a power and a ground. The engine must be cranking to perform this test. You can measure the duty cycle at the signal circuit of the sensor. The duty cycle should be between 45-55 percent for a good sensor.

If the condition is intermittent, refer to Intermittent Conditions.

TEST DESCRIPTION

Steps 1-8:

Steps 9-18:

Steps 19-20:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the fault is present. A hard start is observed when a malfunction is present.
4. This step tests the CMP sensor 12-volt reference circuit from the PCM to the CMP.
5. This step tests the CMP sensor low reference circuit from the PCM to the CMP.
6. This step tests the CMP sensor signal circuit. Applying a voltage causes the CMP signal input high-to-low and low-to-high parameter to increase if the circuit and the PCM are operating properly.
7. This step tests the resistance of the CMP sensor 12-volt reference circuit from the PCM to the CMP sensor.
9. This step tests the resistance of the CMP sensor low reference circuit from the PCM to the CMP sensor.