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 circuit 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 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.
The engine will start if the PCM receives the CKP sensor 24X signal. The PCM can also use the CKP sensor 24X signal in order to determine top dead center (TDC) for all cylinders. The PCM uses the CMP sensor 1X signal in order to determine if the cylinder at TDC is on the firing stroke, or on the exhaust stroke. The system attempts to synchronize the camshaft strokes, and interprets an increase in engine speed as a signal that the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes that the system incorrectly synchronized to the CKP signal. The system 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 the cam signal is stuck low when the signal should be high for 1.5 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
| • | The following conditions may cause this DTC to set: |
| - | Camshaft reluctor wheel damage |
| - | The sensor coming in contact with the reluctor wheel |
| - | Foreign material passing between the sensor and the reluctor wheel |
| • | If you cannot duplicate the DTC, use the Freeze Frame/Failure Records in order to locate an intermittent condition in the following ways: |
| - | Use the information included in the Freeze Frame/Failure Records in order to determine how many miles since the DTC set. |
| - | Use the Fail Counter and Pass Counter in order to determine how many ignition cycles the diagnostic reported as a pass or a fail. |
| - | Operate the vehicle within the same Freeze Frame conditions that you observed in order to isolate when the DTC failed. Use the following conditions for your tests: |
| • | The RPM |
| • | The load |
| • | The vehicle speed |
| • | The temperature |
| • | The CMP sensor output can be tested. The sensor must be supplied with a power and a ground. The engine must be cranking to perform this test. You can measure the duty cycle at the signal circuit of the sensor. The duty cycle should be between 45-55 percent for a good sensor. An internally shorted CAM sensor can pull the 12-volt reference circuit low causing DTC P0335 to set. |
| • | For an intermittent condition, 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 fault is present. A hard start is observed when a malfunction is present.
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This step tests the CMP sensor 12-volt reference circuit from the PCM to the CMP.
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This step tests the CMP sensor low reference circuit from the PCM to the CMP.
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This step tests the CMP sensor signal circuit. Applying a voltage causes the CAM signal input - high to low and low to high parameter to increase if the circuit and the PCM are operating properly.
-
This step tests the CMP sensor 12-volt reference circuit from the PCM to the CMP sensor.
-
This step tests the CMP sensor low reference circuit from the PCM to the CMP 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 | |||||
Does the scan tool parameter increment? | -- | Go to Step 3 | Go to Step 4 | |||||
3 |
Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||
Does the voltage measure near the specified value? | B+ | Go to Step 5 | Go to Step 7 | |||||
Measure the voltage from the CMP sensor 12-volt reference circuit to the CMP sensor low reference circuit with the DMM. Does the voltage measure near the specified voltage? | B+ | Go to Step 6 | Go to Step 9 | |||||
Does the CAM signal input, high-to-low and low-to-high transition counters increment when the test lamp contacts the signal circuit? | -- | Go to Step 15 | Go to Step 10 | |||||
Does the resistance measure within the specified range? | 0-5 ohms | Go to Step 8 | Go to Step 12 | |||||
8 | Inspect the CMP ignition positive voltage circuit for the following conditions:
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||
Does the resistance measure within the specified range? | 0-5 ohms | Go to Step 16 | Go to Step 13 | |||||
10 |
Does the resistance measure within the specified range? | 0-5 ohms | Go to Step 11 | Go to Step 14 | ||||
11 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||
12 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||
13 | Repair the CMP low reference circuit for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
14 | Repair the CMP signal circuit for an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
15 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17 | ||||
16 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 | ||||
17 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
18 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
19 |
Does the DTC run and pass? | -- | Go to Step 20 | Go to Step 2 | ||||
20 | Use a scan tool in order to observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
