Circuit Description
The hall effect camshaft position (CMP) sensor produces 3 ON-OFF pulses for each revolution of the camshaft. The CMP output is pulse width encoded. The electronic control (ECM) module uses the CMP and crankshaft position (CKP) output pulses to determine the engine speed and position. The CMP is connected directly to the ECM by the following circuits:
| • | 12-volt reference |
| • | Low reference |
| • | CMP sensor signal |
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The engine is turning faster than 50 RPM. |
Conditions for Setting the DTC
The ECM does not see a CMP sensor signal for more than 2 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
| • | An intermittent CMP Sensor signal may cause DTC P0340 to set. Wiggle the wiring harness with the engine running and observe the Cam Signal Missed parameter of the scan tool. If the parameter indicates anything other than 0, there is an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections and Inducing Intermittent Fault Conditions in Wiring Systems. |
| • | A short from the 12 volt reference circuit to the Low reference circuit internally in the Camshaft Position (CMP) or Crankshaft Position (CKP) sensor can cause all three DTCs P0336, P0340, and P1345 to set. |
| • | If the CMP Sensor signal is lost while running, the engine will operate normally. If the CMP Sensor signal is not present on start-up, the engine will not start. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If the engine starts and runs, the problem is suspected to be intermittent. If there is a problem with the CMP sensor circuit the vehicle will not run.
-
This step determines if the CMP sensor is working correctly.
-
Inspect the CMP sensor for physical damage. The camshaft may damage the sensor.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Attempt to start the engine. Does the engine start and run? | -- | Go to Diagnostic Aids | Go to Step 3 | |
3 |
Does the DMM display a reading above the specified value? | 10 V | Go to Step 5 | Go to Step 4 |
4 | Connect a DMM between the 12-volt reference and chassis ground. Does the DMM display a reading above the specified value? | 10 V | Go to Step 7 | Go to Step 8 |
5 | Connect a DMM between the CMP sensor signal and a good ground. Does the DMM display the specified value? | 0 V | Go to Step 6 | Go to Step 9 |
Does the DMM display a DC duty cycle within the specified value? | 45-55% | Go to Step 12 | Go to Step 10 | |
7 | Test the low reference circuit for an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
8 | Test the 12-volt reference circuit for an open or a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
9 | Test the CMP signal circuit for a short to voltage or a short to the 12-volt reference circuit. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 |
10 | Test the CMP signal circuit for an open or a short to ground. Refer to Testing for Continuity , Testing for Short to Ground , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
11 | Check for poor connections at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
12 | Check for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 |
|
Important: Inspect the CMP sensor for physical damage before replacing. Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | |
14 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
15 |
Does the DTC run and pass? | -- | Go to Step 16 | -- |
16 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
