Circuit Description
The camshaft position (CMP) sensor works in conjunction with the 1X reluctor trigger wheel on the front of the camshaft gear. The engine control module (ECM) provides a 12-volt reference to the CMP sensor, as well as a low reference and a signal circuit. As the camshaft gear rotates, the reluctor trigger wheel interrupts a magnetic field produced by a magnet within the sensor. The CMP sensor internal circuitry detects this interruption of the magnetic field and produces a signal, which the ECM reads. The 1X signal produced by the CMP sensor is used by the ECM to determine if the cylinder at the top dead center (TDC) is on the firing stroke or the exhaust stroke. The ECM can determine TDC for all cylinders by using the crankshaft position (CKP) sensor 24X signal. If the 1X signal is not received by the ECM, a slightly longer cranking time may be experienced. The ECM will attempt synchronization and looks for an increase in engine speed, indicating that the engine is running. If the ECM does not detect an increase in engine speed, the ECM assumes that it incorrectly synchronized to the exhaust stroke, and then will synchronize to the opposite cam position. If the ECM detects that there is no output signal from the CMP sensor, DTC P0340 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0340 Camshaft Position (CMP) Sensor Circuit
Conditions for Running the DTC
| • | The engine is cranking, or the engine is running. |
| • | DTC P0340 runs continuously when the above condition is met. |
Conditions for Setting the DTC
The ECM detects no CMP sensor output for more than 3 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores the information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/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. |
Diagnostic Aids
DTCs P0335 and P0340 will set with the ignition switch in the Start position if the starter motor is inoperative, or the starter motor control circuit is inoperative. When the ECM enables starter motor operation, the ECM also initiates the diagnostic test routines for DTCs P0335 and P0340. If a condition exists which prevents the engine from cranking, the ECM will not receive a signal input from the crankshaft position (CKP) and the CMP sensors.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 |
Does the CMP sensor active counter number increment? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 4 | ||||||||
Is the voltage within the specified range? | 10-13 V | Go to Step 5 | Go to Step 6 | |||||||||
5 |
Does the CMP sensor active counter number increment? | -- | Go to Step 10 | Go to Step 7 | ||||||||
6 | Test the CMP 12-volt reference circuit between the CMP sensor and the engine control module (ECM) for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||||
7 | Test the CMP low reference circuit between the CMP sensor and the ECM for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | ||||||||
8 | Test the CMP signal circuit between the CMP sensor and the ECM for the following conditions:
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||||
9 | Test for shorted terminals and poor connections at the ECM wire harness electrical connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||
10 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||
11 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 | ||||||||
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||
