Circuit Description
The camshaft position (CMP) sensor is a sensor designed to detect changes in a magnetic field. The control module supplies the CMP sensor with signal and ground circuits. Ignition voltage is supplied to the CMP sensor by an independent circuit. The CMP sensor produces a magnetic field whenever the ignition is ON. The CMP sensor is mounted near a reluctor wheel that is attached to the distributor shaft. When the distributor shaft rotates, or when the engine is cranking or running, the reluctor wheel changes the magnetic field. The CMP sensor converts each change in the magnetic field into a PULSE. The number of teeth on the reluctor wheel determines how many pulses the CMP sensor detects per camshaft rotation. The control module uses the CMP sensor signal in order to calculate the correct timing for sequential fuel injection.
If the VCM does not detect the CMP signal while the engine is running this DTC will be set.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The CMP sensor reference pulse is not detected once every crankshaft revolution.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Electro-magnetic interference from the ignition coil or the spark plugs wire could cause a poor signal condition in the CMP signal circuit to the VCM. Ensure the routing of the CMP sensor circuitry is correct. Also check for the installation of aftermarket accessories and harnesses creating an electro-magnetic interference.
Refer to Symptoms .
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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This step determines if the DTC P0340 is the result of a hard failure or an intermittent condition.
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This step will check for a signal output from the CMP sensor. The signal can also read in AC voltage, approximately 5-7 volts AC.
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If there are not any additional DTCs set, then refer to Diagnostic Aids for examples of conditions that could cause an intermittent loss of signal from the CMP sensor.
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This step determines if there is an open in the ignition positive voltage circuit. If the fuse is the reason for the open, check for a short to ground on the circuit. The open fuse can be caused by a component that shares the same circuit.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the scan tool indicate that this diagnostic Ran and Passed? | -- | |||
3 |
Is the test lamp ON? | -- | ||
4 | Probe the CMP sensor ground circuit at the CMP sensor harness connector with a test lamp connected to B+. Is the test lamp ON? | -- | ||
Important: The red (positive) lead from the DMM must be connected to the 1X CMP sensor signal circuit. Is duty cycle near the specified value? | 50% | |||
6 |
Did you find a problem? | -- | ||
7 | Check for a short to ground or a short to voltage on the 1X CMP sensor signal circuit. Did you find a problem? | -- | ||
This DTC is intermittent. Are any additional DTCs stored? | -- | Go to applicable DTC | Go to Diagnostic Aids | |
Repair the open in the CMP sensor ignition positive voltage circuit . Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | ||
10 | Repair the open in the CMP sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
11 | Check for a poor connection at the CMP sensor. Did you find a problem? | -- | ||
12 | Replace the camshaft position sensor. Refer to Camshaft Position Sensor Replacement . Is the action complete? | -- | -- | |
13 | Check for a poor connection at the VCM. Did you find a problem? | -- | ||
14 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | -- | |
15 |
Important: The replacement VCM must be programmed. Replace the VCM. Refer to VCM Replacement/Programming Is the action complete? | -- | -- | |
16 |
Does the scan tool indicate that the diagnostic Passed? | -- | ||
17 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC | System OK |
