Circuit Description
The Camshaft Position sensor is mounted through the top of the engine block at the rear of the valley cover. The CMP sensor works in conjunction with a 1X reluctor wheel on the camshaft. The reluctor wheel is inside the engine immediately in front of the rear cam bearing. The PCM provides a 12 volt power supply to the CMP sensor as well as a ground 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 Crankshaft Position sensor 24X signal in order to determine crankshaft position and stroke. This diagnostic for the Camshaft Position sensor checks for a loss of Camshaft Position sensor signal.
Observe that as long as the 24X signal is available, the engine starts even if there is no Camshaft Position sensor signal. The PCM can determine when a particular cylinder is on either a firing or exhaust stroke by the 24X signal alone, but the PCM requires the cam signal in order to determine which (firing or exhaust). The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an engine speed increase, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
Conditions for Running the DTC
| • | System voltage is between 9.0 volts and 17.0 volts. |
| • | Engine speed is less than 4000 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 PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important: Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM\TAC modules.
The following mechanical problems may cause this DTC to set:
| • | Poor connections/terminal tension at the sensor |
| • | Camshaft reluctor wheel damage |
| • | The sensor coming in contact with the reluctor wheel |
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies that the fault is present.
-
If the duty cycle is present at the PCM connector, the Camshaft Position sensor B+ reference and ground circuits are OK.
-
This step checks the Camshaft Position sensor B+ reference circuit.
-
This step checks the Camshaft Position sensor ground circuit.
-
This step checks for a short to B+ on the Camshaft Position sensor signal circuit.
-
This step checks for a short to ground on the Camshaft Position sensor signal circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the scan tool parameter increment? | -- | |||
3 |
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | |
Does the DMM display a duty cycle within the specified range? | 45% - 55% | |||
Does the DMM display the specified voltage? | B+ | |||
Measure the voltage from the Camshaft Position sensor B+ reference circuit to the Camshaft Position sensor ground circuit using the DMM J 39200 . Does the DMM display the specified voltage? | B+ | |||
7 |
Did you find and correct the condition? | -- | ||
8 |
Did you find and correct the condition? | -- | ||
Is the voltage less than the specified value? | 1.0V | |||
Probe the Camshaft Position sensor signal circuit using the Test Lamp connected to battery positive voltage. Does the Test Lamp illuminate? | -- | |||
11 |
Is the resistance less than the value specified? | 5ohms | ||
12 | Repair the open or short to ground in the Camshaft Position sensor B+ reference circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
13 | Repair the open in the Camshaft Position sensor ground circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
14 | Repair the short to voltage in the Camshaft Position sensor signal circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
15 | Repair the short to ground in the Camshaft Position sensor signal circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
16 | Repair the open in the Camshaft Position sensor signal circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
17 | Check the connections at the PCM. Refer to Body and Accessories/Wiring Systems. Did you find and correct the condition? | -- | ||
18 |
Important: Before replacing the CMP sensor, inspect the harness connector for proper terminal tension. Refer to Body and Accessories/Wiring Systems. Replace the Camshaft Position sensor. Refer to Camshaft Position Sensor Replacement . Is the action complete? | -- | -- | |
19 |
Important : Program the replacement PCM. Refer to Powertrain Control Module/Throttle Actuator Control Module Replacement . Replace the PCM. Is the action complete? | -- | -- | |
20 |
Does the scan tool indicate that this test ran and passed? | -- | ||
21 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC Table | System OK |
