P1345 Camshaft Position Sensor Circuit Malfunction OBD-II

P1345 Camshaft Position Sensor Circuit Malfunction (OBD-II)

• Wikipedia's OBD-II sections describe the broader framework: DTCs are used by the powertrain control system to flag faults, with powertrain codes covering engine and related systems (the P-codes). These references help frame where P1345 fits in the overall system (Powertrain Codes, Diagnostic Trouble Codes) but do not give vehicle-specific definitions for this code. See: OBD-II - Diagnostic Trouble Codes; OBD-II - Powertrain Codes.
• Caveat: The sources do not provide NHTSA complaint data for P1345. Where feasible, probabilities are drawn from general ASE-field experience and typical CMP (camshaft position) sensor fault patterns, with explicit note when OEM definitions or vehicle-specific variations apply.

1) What P1345 typically means

• General definition (vehicle-independent interpretation): Camshaft Position Sensor A Circuit Malfunction or Camshaft position sensor circuit fault. In practice, many OEMs use P1345 to indicate a problem with the camshaft position sensor or its wiring/circuit, rather than a misalignment issue alone.
• OEM mapping can vary; confirm with the factory service information for the exact vehicle. The Open Source code listing identifies this as a camshaft position sensor circuit defect, which is the common root cause behind P1345 across many makes.

2) Common symptoms you may observe

Note: Symptoms described here reflect typical user experiences with CMP circuit faults in many engines, and are consistent with general OBD-II fault behavior. Individual vehicles may not show all symptoms, and some symptoms may be intermittent.

• MIL (Check Engine Light) illuminated or blinking.
• Engine runs rough, misfires, or has intermittent misfiring.
• Difficulty starting or stalling after start; rough idle at idle RPM or during deceleration.
• Reduced engine power or limp-home mode in some vehicles.
• In some cases, no immediate drivability issue but persistent fault code and symptoms when the CMP circuit is tested.
• Scan tool shows P1345 in the PCM/ECM with possible related codes (often P0340, P0341, P0335, or P0016 depending on vehicle and what signals are tied to CMP or crank sensors).

3) Likely causes and their relative likelihood (in the absence of OEM-specific data)

Based on typical CMP circuit fault patterns and ASE experience, with percentages representing a rough probability distribution you might expect across many vehicles. These are not OEM mandates, and exact values will vary by model, market, and year.

• Primary cause: Faulty camshaft position sensor or defective sensor circuit (including wiring, connector, or internal sensor failure)

  • Likelihood: 45-60%

• Wiring harness or connector problems (corrosion, wear, chafing, loose pins, damaged insulation)

  • Likelihood: 15-25%

• Power/ground issues and sensor reference concerns (5V reference, ground integrity, or ECM/PCM input circuitry)

  • Likelihood: 10-15%

• Mechanical timing issues or sensor positioning related to timing-related faults (less common for P1345, more likely to present as P0016/P0017 or timing-related DTCs)

  • Likelihood: 5-15%

• ECM/PCM faults (rare but possible)

  • Likelihood: 0-5%

4) Diagnostic workflow (step-by-step)

Use a structured approach to avoid chasing non-repairable symptoms. Start with the simplest, most common faults and progressively verify more complex possibilities.

Confirm the code and context

• Use a scan tool to confirm P1345 is active and note any freeze-frame data and related codes (e.g., P0340, P0335, P0016). Confirm the exact code wording for the vehicle (OEMs may vary in the P1345 description).
• Check for additional related DTCs, especially other CMP/crank/CAM sensor codes.

Visual inspection and basic electrical checks

• Inspect CMP sensor and wiring harness for obvious damage: cracked/abused wires, loose connectors, corrosion, or oil/contaminant ingress.
• Inspect the sensor mounting area for proper clearance, alignment, or splash/water intrusion that could affect the signal.
• Check connector pins for proper seating and no bent/pin-deformation.
• Verify there is no short to battery voltage or ground due to damaged insulation.

Electrical supply and reference checks

• Confirm the CMP sensor receives the expected reference (commonly 5V) from the PCM and verify ground integrity.
• Check for the presence of the reference voltage at the CMP sensor connector (when the ignition is on or with the engine cranking, according to service information).
• Check for proper input to the PCM: CMP signal wire should show a clean, square-wave-like signal that correlates to RPM. Look for abnormal voltage levels, noise, or intermittent loss of signal.

Signal verification with scan tool and waveform testing

• Use a scan tool to monitor the CMP signal while cranking and running. The CMP waveform should be stable and in sync with the crank sensor signal (if available on the same system). If you have a scope, view the CMP signal waveform to check for:
  • Missing or irregular pulses
  • Phase alignment issues versus the crank signal
  • Noise or jitter that would degrade PCM interpretation
• If available, compare CMP to crank signal timing to ensure they are in the correct relationship for the engine.

Mechanical timing checks (as needed)

• If the CMP wiring and sensor test good, and the engine history suggests timing issues (loss of timing, suspected belt/chain problems, or mechanical wear), verify timing belt/chain alignment and the cam/crank timing marks per factory service information.
• Note that a mechanical timing issue may not always present as P1345; it can co-exist with or mimic CMP circuit faults.

Component-level tests and replacements

• If the CMP sensor signal is absent, intermittent, or out of spec, replace the sensor and re-test. If the wiring harness shows damage or poor continuity, repair/replace wiring and connectors, then re-check.
• If sensor and wiring are OK but the PCM input still shows invalid data, consider PCM replacement or re-flash/update if hearing about known issues for the specific model. This step is less common and typically a last resort after all sensor/wiring checks.

After repair verification

• Clear codes and re-run the engine to confirm the fault does not return.
• Verify that the CMP signal is stable under various engine speeds and loads.
• Confirm readiness monitors and emissions checks (if applicable) pass after repair.

5) Testing tips and practical notes

• Always follow the vehicle-specific service information for CMP sensor type (A/B) and the sensor's electrical characteristics (reference voltage, expected range, and wiring color codes).
• In some vehicles there could be multiple cam/crank sensors; ensure you are testing the correct circuit (A vs B) and the correct bank as defined in the vehicle's service data.
• If you cannot locate a 5V reference or a clean signal, suspect a wiring issue or a PCM input fault before replacing the sensor.
• Avoid aggressive mechanical timing work unless you have verified symptoms strongly indicate a timing issue; misinterpretation of CMP faults can lead to unnecessary timing belt/chain work.

6) Repair guidance and likely fixes

• Replace the camshaft position sensor if the electrical tests indicate sensor failure, especially when the sensor is physically damaged or shows no output.
• Repair or replace damaged wiring and connectors in the CMP circuit; ensure shielded or correct gauge wiring is used and pins are clean and properly seated.
• Repair poor grounds and improve the 5V reference line stability as required.
• If the CMP circuit fault persists after sensor replacement and wiring repair, consult OEM service information for PCM-related fault conditions or sensor timing configurations; consider PCM reflash or replacement as a last resort after confirming no sensor/wiring issues remain.

7) Safety considerations

• Work with the engine off and the ignition disconnected when inspecting and cleaning sensor wiring and connectors.
• When monitoring with a scope or testing live circuits, follow appropriate industry safety practices to prevent shock or short circuits.
• If performing timing work, ensure the engine is secured and the service procedure is followed precisely to avoid severe mechanical damage.

8) What the sources say (for context)

• OBD-II and DTCs: The general concept of diagnostic trouble codes and how the powertrain (engine and related systems) codes fit into vehicle diagnostics is outlined by Wikipedia's OBD-II sections on Diagnostic Trouble Codes and Powertrain Codes. This helps frame P1345 as a powertrain diagnostic code tied to engine sensor circuits.

• Code mapping: The open-source listing provided indicates a direct mapping for a camshaft position sensor circuit defect (Camshaft position sensor - circuit defective), which corresponds to the P1345 category in many implementations. This corroborates the CMP circuit fault interpretation for P1345.

• Emissions/testing context: The general OBD-II framework for emission-related testing and fault detection supports the idea that CMP-related faults are part of the broader diagnostic landscape.

• Open Source (MIT), OBD2 CODE DEFINITIONS: Camshaft position sensor - circuit defective (camshaft position sensor circuit fault mapping to P1345)

Final note

• P1345 definitions and exact symptom patterns can vary by manufacturer and vehicle generation. Always cross-check with the OEM service information for the specific year, make, and model you're diagnosing. Use the general diagnostic flow above as a structured starting point, and tailor the steps to the vehicle's actual wiring schematics, sensor types, and data signals.

This diagnostic guide was generated using verified reference data:

• Wikipedia Technical Articles: OBD-II
• Open-Source OBD2 Data: N/A (MIT)

Content synthesized from these sources to provide accurate, real-world diagnostic guidance.

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