GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Vibe - AWD 🢒 DTC 🢒 DTC P0340

Circuit Description

The DTC P0340 Camshaft Position (CMP) Sensor Circuit diagnostic monitors the signal from the camshaft position (CMP) sensor. The CMP sensor is a magnetic generator type sensor that produces an AC signal. The CMP sensor signal increases in frequency as the engine RPM increases. The camshaft position signal is used by the powertrain control module (PCM) to determine the optimum ignition timing and the optimum fuel delivery. The CMP sensor is also used to monitor engine misfire and monitor the operation of the CMP actuator system.

Conditions for Setting the DTC
    • No CMP sensor signal is sent to the PCM while cranking.
        OR
    • No CMP sensor signal is sent to the PCM with the engine speed at 600 RPM or more.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL).
    • The PCM stores the conditions which were present when the DTC set as Freeze Frame data.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
    • The DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
    • A DTC can be cleared by using the scan tool Clear DTC Information function.

Diagnostic Aids

Check for any of the following conditions:

    • The camshaft position (CMP) sensor output may be affected by temperature. Inspect the sensors operation and internal resistance at various temperatures. The CMP sensor resistance when cold should be between 835-1,400 ohms at -10 to +50°C (14-122°F). The CMP sensor resistance when hot should be between 1,060-1,645 ohms at 50-100°C (122-212°F).
    • A DTC P0340 that sets while driving and checks OK may be caused by inadequate CMP sensor circuit shielding. Check that the CMP sensor circuit is properly shielded and that the drain wire is fastened securely to ground.

An intermittent malfunction may be caused by a fault in the CMP sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition.

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Powertrain Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Scan Tool Data List, Scan Tool Data Definitions, and Scan Tool Output Controls for scan tool information

Circuit System Verification

    Note: It may take several ignition cycles in order to start the engine.

  1. Engine cranking, or idling, observe the scan tool diagnostic trouble code (DTC) information. DTC P0340 should not be set.
  2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the CMP sensor.
  2. Verify a test lamp illuminates between the low reference circuit terminal 2 and B+.
    3. ⇒ If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
  3. Ignition ON, test for 0.4-0.7 V between the signal circuit terminal 1 and ground.
    4. ⇒If less than the specified range, test the signal circuit for a short to ground, or an open/high resistance. If the circuit tests normal, replace the PCM.
    ⇒ If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the PCM.
  4. Ignition OFF, connect a 3 A fused jumper wire to the CMP signal circuit terminal 1.

    5. Note: It may take several ignition cycles in order to start the engine.

  5. Engine idling, touch the end of the fused jumper wire to ground. The engine should stall.
    6. ⇒If the engine does not stall, replace the PCM.
  6. Inspect the CMP signal rotor for the following:
    7. • A missing or damaged tooth
    • Any foreign material
    • Incorrect installation
    ⇒If a condition is found, repair as necessary.
  7. If all circuits test normal, test or replace the CMP sensor.

Component Testing
  1. Ignition OFF, disconnect the harness connector at the CMP sensor.
  2. Test for 835-1,645 Ω between the terminals of the CMP sensor.
    3. ⇒If not within the specified range, replace the CMP sensor.
  3. Engine idling, test for approximately 1 V AC between the terminals of the CMP sensor.
    4. ⇒If not within the specified range, replace the CMP sensor.
  4. Raise the engine speed to 3,000 RPM. The AC voltage should increase to greater than 4.5 V.
    5. ⇒If not within the specified range, replace the CMP sensor.

Repair Instructions
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text. Verify the DTC does not reset.

Camshaft Position Sensor Replacement