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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 DTS 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 DTC P0340 or P0341

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptors

DTC P0340: Camshaft Position (CMP) Sensor Circuit

DTC P0341: Camshaft Position (CMP) Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

5-Volt Reference Circuit

P0340, P0641, P0452

P0340

P0641

--

CMP Sensor Signal Circuit

P0340

P0340

P0341

P0341

Low Reference Circuit

--

P0340

--

--

Typical Scan Tool Data

CMP Sensor

Circuit

Normal Range

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine Running

5-Volt Reference Circuit

Same as Engine Speed

0 RPM

0 RPM

0 RPM

CMP Sensor Signal Circuit

Same as Engine Speed

0 RPM

0 RPM

0 RPM

Low Reference Circuit

Same as Engine Speed

Same as Engine Speed

0 RPM

Same as Engine Speed

Circuit/System Description

The 4X camshaft position (CMP) sensor circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, low reference circuit, and an output signal circuit. The CMP sensor is an internally magnetic biased digital output integrated circuit sensing device. The sensor detects magnetic flux changes of the teeth and slots of a 4-tooth reluctor wheel attached to the camshaft. As each reluctor wheel tooth rotates past the CMP sensor, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF DC voltage pulse of varying frequency, with 4 varying width output pulses per camshaft revolution that represent an image of the camshaft reluctor wheel. The frequency of the CMP sensor output depends on the velocity of the camshaft. The ECM decodes the narrow and wide tooth pattern to identify camshaft position. This information is then used to determine the optimum ignition and injection points of the engine. The ECM also uses CMP sensor output information to determine the camshaft relative position to the crankshaft, to control camshaft phasing, and for limp-home operation.

Conditions for Running the DTC
    • DTC P0641 or P0651 is not set.
    • The engine is cranking or running.
    • The DTCs run continuously when the above conditions are met.

Conditions for Setting the DTC

P0340

       Important: The ECM detects engine movement by sensing the airflow through the MAF sensor is more than 3 g/s, or by sensing CKP sensor pulses.

    • The ECM detects that the starter is commanded on and the engine has been cranking for more than 4 seconds without a CMP sensor pulse.
        OR
    • The ECM detects that the engine has started, but did not received a CMP sensor pulse during the first engine revolution.
        OR
    • The ECM detects that the engine is running, but does not receive a CMP sensor pulse for 800 of 1000 engine cycles.

P0341

       Important: The ECM detects engine movement by sensing the airflow through the mass air flow (MAF) sensor is more than 3 g/s, or by sensing crankshaft position (CKP) sensor pulses.

    • The ECM detects that the engine has started, but has received either of the following during the first engine revolution:
       - Less than or more than 4 CMP sensor pulses, if equipped with an automatic transmission
       - less than 4 or more than 6 CMP sensor pulses, if equipped with a manual transmission
       - OR
    • The ECM detects that the engine is running, but receives less than 397 CMP or more than 403 CMP sensor pulses per 100 engine cycles in 800 of 1000 engine cycles.

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

Inspect the 10-way engine harness to fuel injector harness connector, the CMP sensor connector, and the ECM connector for corrosion.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views
    •  Inline Harness Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification
  1. With the engine running, observe the CMP Sensor parameter using the scan tool. The CMP Sensor speed should match the Engine Speed parameter within 100 RPM.
    2. ⇒If the CMP Sensor speed is 0, continue with Circuit/System Testing.
  2. With the ignition ON and the engine OFF, use the Live Plot function on the scan tool. Select the Engine Speed parameter and the CMP Sensor parameter. Change the minimum spec to 0 RPM for both parameters. Change the maximum spec to 1,500 RPM for both parameters.
  3. Observe the scan tool and start the engine. The graphed lines should stay together.
    4. ⇒If the CMP sensor line deviates excessively from the engine speed line, continue with Circuit/System Testing.
  4. With the engine running, use the Live Plot function on the scan tool. Select the Engine Speed parameter and the CMP Sensor parameter. Change the minimum spec to 400 RPM for both parameters. Change the maximum spec to 3,000 RPM for both parameters.
  5. Observe the scan tool and operate the vehicle under 3,000 RPM within the Conditions for Running the DTC. The graphed lines should stay together.
    6. ⇒If the CMP Sensor line deviates excessively from the engine speed line, continue with Circuit/System Testing.
  6. With the engine running, use the Live Plot function on the scan tool. Select the Engine Speed parameter and the CMP Sensor parameter. Change the minimum spec to 3,000 RPM for both parameters. Change the maximum spec to 5,500 RPM for both parameters.
  7. Observe the scan tool and operate the vehicle, between 3,000-5,500 RPM, within the Conditions for Running the DTC. The graphed lines should stay together.
    8. ⇒If the CMP Sensor line deviates excessively from the engine speed line, continue with Circuit/System Testing.
  8. Engine running, observe the DTC information with a scan tool. DTCs P0340 or P0341 should not set.
  9. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing
  1. With the ignition OFF, Inspect the engine wiring harnesses carrying the CMP sensor circuits for the following conditions:
    2. • Close routing of aftermarket electrical equipment
    • Close to solenoids, motors, and relays
    ⇒Correct any wire harness routing or component placement conditions, if it is determined to be a possible source of electrical interference.
  2. Disconnect the cam sensor.
  3. With the ignition ON and the engine OFF, measure for 4.8-5.2 volts at the ECM side of the connector between the 5-volt reference circuit of the CMP sensor and a good ground.
    4. ⇒If the voltage is less than 4.8 volts, test for an open in the 5-volt reference circuit. If the circuit tests normal, replace the control module.
  4. With the ignition ON and the engine OFF, measure for 4.8-5.2 volts at the ECM side of the connector between the CMP sensor signal circuit and a good ground.
    5. ⇒If the voltage is less than 4.8 volts, test for an open or a short to ground in the CMP sensor signal circuit. If the circuit tests normal, replace the control module.
    ⇒ If the voltage is more than 5.2 volts, test for a short to voltage in the CMP sensor signal circuit. If the circuit tests normal, replace the control module.
  5. With the ignition ON and the engine OFF, measure for 1-3 mA, at the ECM side of the connector between the CMP sensor signal circuit and a good ground.
    6. ⇒If the amperage is more than 3 mA, test the CMP sensor signal circuit for a short to the 5-volt reference circuit. If the circuit tests normal, replace the control module.
  6. Connect a fused jumper wire to a good ground.
  7. With the ignition ON and the engine OFF, observe the CMP Sensor parameter on the scan tool.
  8. Touch the jumper wire to the CMP sensor signal circuit repeatedly at the ECM side of the connector. The CMP Sensor parameter should display a value other than 0 RPM.
    9. ⇒If the CMP Sensor parameter displays 0 RPM, replace the ECM.
  9. With the ignition ON and the engine OFF, measure for B+ at the ECM side of the connector between the low reference circuit of the CMP sensor and the battery positive post.
    10. ⇒If the voltage measured between the low reference circuit and the battery positive post is not the same as voltage measured between a good ground and the battery positive post, test for an open/high resistance in the low reference circuit. If the circuit tests normal, replace the control module.
  10. With the ignition OFF, inspect the wiring harness to the CMP sensor, for any damage, opens, or shorts.
    11. ⇒Repair any wiring or connector damage, if necessary.
  11. Inspect the CMP sensor for looseness. Remove the CMP sensor from the engine and inspect the sensor and the O-ring for damage.
    12. ⇒Repair or replace the CMP sensor, if necessary.
  12. Reconnect the CMP sensor to the harness.
  13. Turn ON the ignition, with the engine OFF.
  14. While observing the CMP Sensor and CMP Active Counter parameters on the scan tool, pass a steel object by the tip of the sensor repeatedly. The CMP Active Counter parameter should increment and the CMP Sensor parameter should display a value other than 0 RPM.
    15. ⇒If the parameters remain at 0, replace the CMP sensor.
  15. Inspect the reluctor wheel for damage.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Camshaft Position Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming