DTC Descriptors
DTC P0366: Exhaust Camshaft Position (CMP) Sensor Performance Bank 1
DTC P0391: Exhaust Camshaft Position (CMP) Sensor Performance Bank 2
Circuit/System Description
The 4X camshaft position (CMP) sensor circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, low reference circuit, and an output signal circuit. The CMP sensor is an internally magnetic biased digital output integrated
circuit sensing device. The sensor detects magnetic flux changes of the teeth and slots of a 4-tooth reluctor wheel attached to the camshaft. As each reluctor wheel tooth rotates past the CMP sensor, the resulting change in the magnetic field is used by the
sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF DC voltage pulse of varying frequency, with 4 varying width output pulses per camshaft revolution that represent an image of the camshaft reluctor wheel. The frequency
of the CMP sensor output depends on the velocity of the camshaft. The ECM decodes the narrow and wide tooth pattern to identify camshaft position. This information is then used to determine the optimum ignition and injection points of the engine. The ECM also
uses CMP sensor output information to determine the camshaft relative position to the crankshaft, to control camshaft phasing.
Conditions for Running the DTC
| • | DTC P0366 or P0391 runs continuously when the above condition is met. |
Conditions for Setting the DTC
The ECM detects a signal from the CMP sensor, but the number of pulses are less than or more than what is expected during one crankshaft revolution for more than 1 second.
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 DTC
| • | The control module turns OFF the 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. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
If P0366 or P0391 is set, continue with Circuit/System Testing.
Circuit/System Testing
- With the ignition OFF, inspect the engine wiring harnesses carrying the CMP sensor circuits for the following conditions:
| • | Close routing of secondary ignition wires |
| • | Close routing of aftermarket electrical equipment |
| • | Close to solenoids, motors, and relays |
| ⇒ | Correct any wire harness routing or component placement conditions, if it is determined to be a possible source of electrical interference. |
- Remove the affected CMP sensor. Inspect the CMP sensor and the camshaft actuator reluctor wheel for the following conditions.
| • | Incorrect sensor installation |
| • | A cracked or damaged sensor |
| • | The sensor coming in contact with the reluctor wheel |
| • | Excessive air gap between the reluctor wheel and the sensor |
| • | Foreign material passing between the sensor and the camshaft reluctor wheel |
| • | Camshaft reluctor wheel damage |
| ⇒ | If you find a condition with the CMP sensor or the camshaft reluctor wheel, repair as necessary. |
| ⇒ | If a condition is not found replace the affected CMP sensor. |
Repair Instructions
Always perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
