Circuit Description
The camshaft position (CMP) sensor is a hall effect switching device that works in conjunction with a single tooth reluctor wheel used to determine the position of the bank 2 exhaust camshaft. The engine control module (ECM) expects the CMP sensor signal to be low, 0 volts, as the single tooth in the reluctor wheel passes the sensor, and high, 12 volts, during the remainder of the reluctor wheel rotation. The ECM supplies a 12-volt pull up voltage on the CMP sensor signal circuit. The ECM expects to see one transition from high to low every two crankshaft revolutions. This signal, when combined with the crankshaft position (CKP) sensor signal, enables the ECM to properly synchronize ignition timing, fuel delivery and knock control. As long as the CKP signal is available, the engine can start and run. The ECM will default to a non-sequential fuel injector operation even if there is no CMP sensor signal. If the ECM detects continuously high signal transitions within a certain number of crankshaft revolutions, DTC P0343 sets.
The CMP sensor has the following circuits:
| • | Ignition 1 voltage circuit |
| • | Low reference circuit |
| • | CMP sensor signal circuit |
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The CMP sensor signal is continuously high for eight or more crankshaft revolutions.
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 for proper installation |
| - | The sensor coming in contact with the reluctor wheel |
| - | Excessive air gap between the reluctor wheel and the sensor magnet |
| - | A cracked or damaged sensor |
| - | Foreign material passing between the sensor and the reluctor wheel |
| Notice: Do not use a test lamp in order to test the continuity of the low reference circuit. Damage to the Engine Control Module (ECM) will result. |
| • | If an intermittent condition exists, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the fault is present.
-
This step determines if the fault is in the ignition 1 voltage circuit or the low reference circuit.
-
This step tests the CMP sensor signal circuit. Applying a ground causes the CMP signal Active Counter to increment when the circuit is touched if the circuit and the ECM are operating properly.
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-Engine Controls? | -- | Go to Step 2 | |
Does the CMP Active Counter increment? | -- | Go to Step 3 | Go to Step 4 | |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Notice: Do not use a test lamp in order to test the continuity of the low reference circuit. Damage to the Engine Control Module (ECM) will result.
Is the voltage near the specified value? | B+ | Go to Step 6 | Go to Step 5 |
Measure the voltage from the ignition 1 voltage circuit of the CMP sensor connector to a good ground with a DMM. Is the voltage near the specified value? | B+ | Go to Step 9 | Go to Step 8 | |
Momentarily and repeatedly probe the CMP sensor signal circuit at the CMP sensor with a test lamp connected to a good ground. Does the CMP Active Counter increment each time the test lamp contacts the circuit? | -- | Go to Step 12 | Go to Step 7 | |
7 | Probe the signal circuit of the CMP sensor with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 10 |
8 | Test the CMP sensor ignition 1 voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | -- |
9 | Test the CMP sensor low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
10 | Test the CMP sensor signal circuit for a open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
11 |
Important:: Disconnecting the ECM may remove the short from the circuit. Test the CMP sensor signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
12 | Test for an intermittent and for a poor connection at the CMP sensor . Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 |
13 | Test for an intermittent and for a poor connection at the ECM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 |
14 |
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15 |
15 |
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 16 |
16 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
17 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
18 |
Does the DTC fail this ignition? | -- | Go to Step 19 | Go to Step 2 |
19 | Observe the Capture Info with a scan tool. Are there any DTC's that have not been diagnosed? | -- | System OK | |
