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 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 1X signal in combination with the crankshaft position (CKP) sensor 24X signal in order to determine crankshaft position and stroke. This diagnostic for the CMP sensor checks for a loss of CMP sensor signal.
Observe that as long as the PCM receives the CKP sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the CKP sensor 24X signal alone. The CMP 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 assumes it 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 that a CMP to CKP mis-match has occurred.
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 |
| • | A cracked or damaged sensor |
| • | Foreign material passing between the sensor and reluctor wheel |
If you find damage to the reluctor wheel or camshaft, refer to Camshaft Replacement in Engine Mechanical - 8.1L.
If the condition is suspected to be intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step verifies that the malfunction is present. A hard start is observed when a malfunction is present.
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This step inspects for electromagnetic interference (EMI) on the CMP sensor circuits.
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Damage to the face of the sensor could indicate foreign material passing between the CMP sensor and the reluctor wheel. This condition would cause this DTC to set. Damage to the reluctor wheel would affect the CMP sensor output.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |||||||
|
Important:: If there are any other CMP DTCs set, diagnose those DTCs first.
Does the scan tool indicate that DTC P0341 failed this ignition? | Go to Step 3 | Go to Diagnostic Aids | |||||||
Did you find and correct the condition? | Go to Step 8 | Go to Step 4 | |||||||
4 |
Did you find and correct the condition? | Go to Step 8 | Go to Step 5 | ||||||
5 |
Did you find and correct the condition? | Go to Step 8 | Go to Step 6 | ||||||
Does the CMP sensor show signs of damage? | Go to Diagnostic Aids | Go to Step 7 | |||||||
7 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the replacement? | Go to Step 8 | -- | ||||||
8 |
Does the DTC run and pass? | Go to Step 9 | Go to Step 2 | ||||||
9 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK | |||||||
