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Camshaft Position Sensor Circuit Malfunction: Diagnosing Error Codes P0340 & P0344

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The camshaft position sensor (CMP) is a critical component in your vehicle’s engine management system. It monitors the position of the camshaft, providing essential data to the powertrain control module (PCM) for precise fuel injection and ignition timing. When the PCM detects a problem with the CMP sensor circuit, it can trigger diagnostic trouble codes (DTCs) like P0340 (Camshaft Position Sensor A Circuit Malfunction) and P0344 (Camshaft Position Sensor A Circuit Intermittent). These codes indicate a malfunction in the electrical circuit of the camshaft position sensor, which can lead to various engine performance issues, including difficulty starting or even a no-start condition.

This comprehensive guide, based on Ford Motor Company’s diagnostic procedures, will walk you through the steps to effectively diagnose and address a Camshaft Position Sensor Circuit Malfunction. Whether you are a seasoned automotive technician or a dedicated DIYer, understanding these steps is crucial for resolving these common OBD-II trouble codes.

Understanding DTCs P0340 and P0344: Camshaft Position Sensor Circuit Issues

DTC P0340 and P0344 specifically point to problems within the camshaft position sensor “A” circuit, typically referring to Bank 1 or a single sensor system. Let’s break down what each code signifies:

  • P0340 – Camshaft Position Sensor A Circuit (Bank 1 or single sensor): This code is set when the PCM loses the camshaft position sensor signal entirely. This is a hard fault, meaning the signal is consistently absent.

  • P0344 – Camshaft Position Sensor A Circuit Intermittent (Bank 1 or single sensor): This code indicates that the PCM is receiving an inconsistent or fluctuating signal from the CMP sensor. This is an intermittent fault, meaning the problem occurs sporadically.

Both codes can stem from a range of issues within the sensor circuit, not necessarily a faulty sensor itself. Pinpointing the root cause requires a systematic diagnostic approach.

Possible Causes of Camshaft Position Sensor Circuit Malfunction

Before jumping to sensor replacement, it’s crucial to consider all potential causes for a camshaft position sensor circuit malfunction. These can be broadly categorized as follows:

  • Electrical Circuit Problems:

    • Open Circuit: A break in the wiring preventing signal flow.
    • Short to Ground: A wire is inappropriately contacting the vehicle’s chassis ground.
    • Short to Voltage: A wire is inappropriately contacting a voltage source.
    • SIG RTN Open (VR Sensor): Signal Return circuit issue specific to Variable Reluctance (VR) sensors.
    • CMP GND Open (Hall-effect Sensor): Camshaft Position Sensor Ground issue specific to Hall-effect sensors.
    • Short to CMP2 Circuit: (If equipped with a second camshaft sensor) Short circuit between CMP sensor circuits.

  • Sensor Related Issues:

    • Incorrect CMP Sensor Installation: Improper installation, especially with Hall-effect sensors, can disrupt signal generation.
    • Damaged CMP Sensor Shielding: Shielding protects the sensor signal from electrical interference. Damage can lead to signal disruption.
    • Damaged CMP Sensor: The sensor itself may be faulty due to wear, damage, or internal failure.

  • PCM or System Issues:

    • Damaged PCM: In rare cases, the PCM itself may be the source of the problem.
    • External Electrical Interference: Harness routing issues, modifications, or interference from other vehicle systems can disrupt the CMP signal.

Generator B+ Connector Location: Disconnecting this connector is part of testing for excessive electrical noise from the generator, a potential cause of CMP sensor circuit malfunction.

Diagnostic Steps: Pinpoint Test DR for DTCs P0340 and P0344

The following pinpoint test, adapted from Ford’s diagnostic manual, provides a structured approach to diagnosing camshaft position sensor circuit malfunction and related DTCs P0340 and P0344. Follow these steps in order for efficient troubleshooting.

DR1: Check for Diagnostic Trouble Codes (DTCs)

  • Use an OBD-II scanner to retrieve DTCs from the PCM.
  • Are DTCs P0340, P0344, P0345, or P0349 present?
    • Yes: Proceed to DR2. (P0345 and P0349 refer to Camshaft Position Sensor “B” Circuit Malfunction, also covered in this pinpoint test).
    • No: Refer to the vehicle’s specific diagnostic trouble code charts and descriptions for other DTCs present.

DR2: Continuous Memory DTCs P0340, P0344, P0345, and P0349: Check if the Engine Starts

  • Attempt to start the engine.
  • Does the engine start?
    • Yes: Proceed to DR3.
    • No:
      • For symptoms without DTCs, consult symptom charts for further direction.
      • For vehicles with DTCs and a no-crank symptom, proceed to DR19 (later step addressing Hall-effect sensors and power supply issues).
      • For all other no-start scenarios with these DTCs, proceed to DR3.

DR3: Clear and Attempt to Retrieve the DTC

  • Important Notes:
    • Consider ignition, alternator noise, RFI (Radio Frequency Interference), and CKP (Crankshaft Position Sensor) concerns if DTCs P0340, P0344, P0345, or P0349 are present.
    • For vehicles with Variable Camshaft Timing (VCT), low engine oil level, oil filter issues, oil contamination, or VCT system problems can cause camshaft positioning errors.
  • Ignition ON, Engine OFF.
  • Clear PCM DTCs using the OBD-II scanner.
  • Ignition ON, Engine Running.
  • Increase engine speed to over 1500 RPM for 10 seconds. Repeat this three times.
  • Perform a PCM self-test using the scanner.
  • Are DTCs P0340, P0344, P0345, or P0349 present again?
    • Yes: Proceed to DR4.
    • No: Proceed to Pinpoint Test Z (not detailed here, generally indicates intermittent issue or resolved fault).

DR4: Check the Generator for Excessive Electrical Noise

  • Note: Generator/regulator electrical noise might decrease when the B+ connector is disconnected.
  • PCM connector connected.
  • CMP Sensor connector connected.
  • Ignition ON, Engine Running.
  • Listen for audible electrical noise from the generator.
  • Ignition OFF.
  • Disconnect the Generator/regulator B+ connector.
  • Ignition ON, Engine Running.
  • With the engine running, check if generator noise persists.
  • Does the noise remain constant when the B+ connector is disconnected?
    • Yes:
      • For continuous memory DTCs P0340 or P0344, proceed to DR5.
      • For continuous memory DTCs P0345 or P0349, proceed to DR13.
    • No: Refer to the Workshop Manual Section 414-00, Charging System, to diagnose a noisy generator.

DR5: Determine the CMP Sensor Physical Type

  • Ignition OFF.
  • Is the CMP sensor a synchronizer (gear-driven) type? (Visually inspect the sensor and its mounting).
    • Yes: Proceed to DR6.
    • No: Proceed to DR7.

DR6: Verify Correct Installation of the CMP Sensor

  • Note: An improperly installed CMP sensor can misidentify cylinder 1 power stroke, leading to tip-in hesitation and DTC P0340.
  • Is the CMP sensor installed correctly? (Refer to vehicle-specific repair manual for CMP sensor installation procedures).
    • Yes: Proceed to DR7.
    • No:
      • Install the CMP sensor correctly. Refer to the Workshop Manual Section 303-14, Electronic Engine Controls for Camshaft Synchronizer removal and installation procedures.
      • Clear DTCs and repeat the self-test (DR3).

DR7: Determine the CMP Sensor Electronic Type

  • Note: VR (Variable Reluctance) sensors typically have 2-wire connectors, while Hall-effect sensors have 3-wire connectors.
  • Is the CMP sensor a VR type? (Inspect the sensor connector for the number of wires).
    • Yes: Proceed to DR8.
    • No: The CMP sensor is a Hall-effect type. Proceed to DR19.

DR8: Continuous Memory DTCs P0340 and P0344: Check CMP Sensor Resistance (VR Sensors)

  • Note: For 2-pin CMP sensors (VR type), measure resistance between the specified circuits.

  • Ignition OFF.

  • CMP Sensor connector disconnected.

  • Measure resistance using a digital multimeter (DMM):

    ( + ) DMM Lead – CMP Sensor Connector, Component Side ( – ) DMM Lead – CMP Sensor Connector, Component Side
    CMP SIGRTN or VRSRTN
    Vehicle Minimum Resistance (ohms) Maximum Resistance (ohms)
    Edge, MKX (3.5L) 586 2,033

  • Is the resistance within specification?

    • Yes: Proceed to DR9.
    • No:
      • Install a new CMP sensor. Refer to Workshop Manual Section 303-14, Electronic Engine Controls.
      • Clear DTCs and repeat the self-test (DR3).

DR9: Check CMP Circuit for Short to Voltage in Harness (VR Sensors)

  • PCM connector disconnected.

  • Ignition ON, Engine OFF.

  • Measure voltage using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – Vehicle Battery
    CMP Negative terminal

  • Is the voltage less than 1V?

    • Yes: Proceed to DR10.
    • No:
      • Repair the short circuit to voltage.
      • Clear DTCs and repeat the self-test (DR3).

DR10: Check CMP and SIGRTN/VRSRTN Circuits for Open in Harness (VR Sensors)

  • Note: For 2-pin CMP sensors, measure applicable circuits.

  • Ignition OFF.

  • Measure resistance using DMM:

    ( + ) DMM Lead – PCM Connector, Harness Side ( – ) DMM Lead – CMP Sensor Connector, Harness Side
    CMP CMP
    SIGRTN SIGRTN or VRSRTN
    VRSRTN VRSRTN (if applicable)

  • Are the resistances less than 5 ohms?

    • Yes: Proceed to DR11.
    • No:
      • Repair the open circuit.
      • Clear DTCs and repeat the self-test (DR3).

DR11: Check for Short in Harness Between PCM and CMP Sensor (VR Sensors)

  • Note: For 2-pin CMP sensors, measure applicable circuits.

  • Measure resistance using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – CMP Sensor Connector, Harness Side
    CMP SIGRTN or VRSRTN

  • Measure resistance using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – Vehicle Battery
    CMP Negative terminal
    SIGRTN Negative terminal or VRSRTN
    VRSRTN Negative terminal (if applicable)

  • Are the resistances greater than 10K ohms?

    • Yes: Proceed to DR12.
    • No:
      • Repair the short circuit.
      • Clear DTCs and repeat the self-test (DR3).

DR12: Check CMP Sensor Output (VR Sensors)

  • Note: For 2-pin CMP sensors, measure applicable circuits. For 3-pin (Hall-effect) sensors, refer to DR25.

  • Ignition OFF.

  • Generator/regulator B+ connector connected.

  • CMP Sensor connector disconnected.

  • Ignition ON, Engine Running.

  • Set DMM to low voltage AC scale.

  • Measure voltage using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Component Side ( – ) DMM Lead – CMP Sensor Connector, Component Side
    CMP SIGRTN or VRSRTN

  • Run engine at approximately 2500 RPM.

  • Is the voltage greater than 0.25V AC?

    • Yes: Proceed to DR26 (VCT System Check).
    • No:
      • Install a new CMP sensor. Refer to Workshop Manual Section 303-14, Electronic Engine Controls.
      • Clear DTCs and repeat the self-test (DR3).

(Steps DR13 – DR18 are for DTCs P0345 & P0349, related to CMP Sensor 2, and follow similar logic to DR8-DR12. For brevity and focus on P0340/P0344 and single sensor systems, these steps are summarized below):

  • DR13-DR18 (CMP2 Sensor – if applicable): These steps are analogous to DR8-DR12 but apply to the second camshaft position sensor (CMP2), if your vehicle is equipped with one. They involve checking resistance, shorts, and sensor output for CMP2, following the same diagnostic principles as for CMP sensor 1.

DR19: Continuous Memory DTCs P0340 and P0344: Check Voltage to CMP Sensor (Hall-effect Sensors)

  • Note: For 3-pin CMP sensors (Hall-effect), check voltage supply.

  • CMP Sensor connector disconnected.

  • Ignition ON, Engine OFF.

  • Measure voltage using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – Vehicle Battery
    VPWR or VBPWR Negative terminal

  • Is the voltage greater than 10V?

    • Yes: Proceed to DR21.
    • No:
      • For F-150, repair the open circuit in VPWR or VBPWR. Clear DTCs and repeat self-test (DR3).
      • For other vehicles, proceed to DR20.

DR20: Check VBPWR Circuit for Short to Ground (Hall-effect Sensors)

  • Note: If circuit DTCs are set due to multiple component issues, check for common causes like SIGRTN, VREF, VPWR, or VBPWR.

  • Ignition OFF.

  • Measure resistance using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – Ground
    VBPWR Ground

  • Is the resistance greater than 10K ohms?

    • Yes: Repair the open circuit in VBPWR. Clear DTCs and repeat self-test (DR3).
    • No: Repair the short to ground in VBPWR. Clear DTCs and repeat self-test (DR3).

DR21: Check PWRGND or SIGRTN Circuit for Open Circuit in Harness (Hall-effect Sensors)

  • Note: For 3-pin CMP sensors, check ground/signal return circuit continuity.

  • Ignition OFF.

  • Measure voltage using DMM:

    ( + ) DMM Lead – Vehicle Battery ( – ) DMM Lead – CMP Sensor Connector, Harness Side
    Positive terminal PWRGND or SIGRTN

  • Is the voltage greater than 10V?

    • Yes: Proceed to DR22.
    • No: Repair the open circuit in PWRGND or SIGRTN. Clear DTCs and repeat self-test (DR3).

DR22: Check CMP Circuit for Short to Voltage in Harness (Hall-effect Sensors)

  • PCM connector disconnected.

  • Ignition ON, Engine OFF.

  • Measure voltage using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – Vehicle Battery
    CMP Negative terminal

  • Is the voltage less than 1V?

    • Yes: Proceed to DR23.
    • No: Repair the short circuit to voltage. Clear DTCs and repeat self-test (DR3).

DR23: Check for Open Circuit Between PCM and CMP Sensor (Hall-effect Sensors)

  • Ignition OFF.

  • CMP Sensor connector disconnected.

  • Measure resistance using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – PCM Connector, Harness Side
    CMP CMP

  • Is the resistance less than 5 ohms?

    • Yes: Proceed to DR24.
    • No: Repair the open circuit. Clear DTCs and repeat self-test (DR3).

DR24: Check CMP Circuit for Short to PWRGND or SIGRTN in Harness (Hall-effect Sensors)

  • Note: Measurement can be taken at PCM or CMP connector for easier access.

  • Measure resistance using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Harness Side ( – ) DMM Lead – CMP Sensor Connector, Harness Side
    CMP PWRGND or SIGRTN

  • Is the resistance greater than 10K ohms?

    • Yes: Proceed to DR25.
    • No: Repair the short circuit. Clear DTCs and repeat self-test (DR3).

DR25: Check CMP Sensor for Correct Operation (Hall-effect Sensors)

  • Note: For 3-pin CMP sensors, this step checks sensor signal switching.

  • PCM connector connected.

  • Connect a 5 amp fused jumper wire as follows:

    Point A – CMP Sensor Connector, Harness Side Point B – CMP Sensor Connector, Component Side
    VPWR or VBPWR VPWR or VBPWR
    SIGRTN or PWRGND SIGRTN or PWRGND

  • Ignition ON, Engine Running.

  • Set DMM to low voltage DC scale.

  • Measure voltage using DMM:

    ( + ) DMM Lead – CMP Sensor Connector, Component Side ( – ) DMM Lead – Vehicle Battery
    CMP Negative terminal

  • Does the voltage switch between LOW (less than 2V DC) and HIGH (greater than 8V DC)?

    • Yes: Proceed to DR27 (PCM Check).
    • No: Install a new CMP sensor. Refer to Workshop Manual Section 303-14, Electronic Engine Controls. Clear DTCs and repeat self-test (DR3).

DR26: Check the Variable Camshaft Timing (VCT) System

  • Note: Only diagnose the VCT system on the bank indicated by the DTC.
  • Check the VCT system for correct mechanical and hydraulic operation.
  • Is a VCT concern present?
    • Yes: Repair VCT system as necessary. Clear DTCs and repeat self-test (DR3).
    • No: Proceed to DR27.

DR27: Check for Correct PCM Operation

  • Disconnect all PCM connectors.
  • Visually inspect PCM connectors for:
    • Pushed out pins
    • Corrosion
  • Reconnect all PCM connectors, ensuring they are securely seated.
  • Perform PCM self-test and verify if the concern persists.
  • Is the concern still present?
    • Yes: Install a new PCM. Refer to Section 2, Flash EEPROM, Programming the VID Block for Replacement PCM (refer to vehicle-specific service manual for PCM replacement and programming).
    • No: The system is currently operating correctly. The issue may have been due to a loose or corroded connector.

CMP Sensor Connector Details 1: Diagram showing the connector pinout for a camshaft position sensor, crucial for performing accurate circuit tests during diagnostics.

CMP Sensor Connector Details 2: Further connector details for another camshaft position sensor, highlighting the importance of using correct wiring diagrams during fault finding.

Conclusion: Resolving Camshaft Position Sensor Circuit Malfunctions

Diagnosing a camshaft position sensor circuit malfunction requires a methodical approach. By following this pinpoint test DR, you can systematically eliminate potential causes, from simple wiring issues to sensor failure or even PCM problems. Remember to always consult your vehicle’s specific repair manual for detailed procedures and specifications. Accurate diagnosis and repair will ensure your engine runs smoothly and efficiently, resolving those frustrating P0340 and P0344 error codes.

Disclaimer: This guide is for informational purposes only and based on publicly available information. Always consult a qualified automotive technician for diagnosis and repair of vehicle issues. Ford Motor Company is the copyright holder of the original diagnostic procedures.

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