Comprehensive Diagnostic Guide for P0368

Code: P0368 - Camshaft Position Sensor B Bank 1 - Circuit High Input

What This Code Means

• P0368 is a powertrain diagnostic trouble code indicating a high-input condition on the Camshaft Position Sensor (CMP) Bank 1, Sensor B circuit. In modern engines, CMP sensors (A and B) provide the ECU with cam timing information. A "Circuit High Input" fault means the ECU is seeing an abnormally high voltage on the CMP B signal line (Bank 1), which may indicate a sensor fault, wiring issue, or ECU input problem.
• Context from sources:
  • OBD-II framework defines how DTCs are used by the PCM/ECU to monitor engine timing and other powertrain parameters (Diagnostic Trouble Codes; Powertrain Codes) and that these codes relate to emissions and engine-control systems. This establishes that P0368 is a powertrain timingsensor fault, tracked by the PCM.
  • A specific open-source description labels the issue as (High input signal for CMP Sensor B Bank 1), which matches P0368's intended meaning in many vehicle platforms.
  • Taken together, P0368 points to the Bank 1 Camshaft Position Sensor B circuit reading higher than expected voltage, prompting a check of CMP B, its wiring, or the PCM input.

Symptoms

• Check Engine Light (SES/MIL) is illuminated.
• Engine runs rough, misfires, or runs inconsistently at idle or low speed.
• Engine may stall or be hard to start; occasional hesitation or lack of power under load.
• Reduced fuel economy or driveability issues, especially around idle and low RPM ranges.
• Some vehicles may not start or run properly until a fault is cleared or the sensor/wiring is repaired.

Note: Symptom patterns for DTCs like P0368 correlate with camshaft sensing issues and timing-related sensor inputs. If P0368 appears together with other CMP-related codes (e.g., P0335, P0340-P0344) or with P030x misfire codes on Bank 1, it strengthens suspicion of CMP-B circuit/sensor issues or related wiring.

Probable Causes

• Faulty CMP Sensor B (Bank 1) itself: 40-50%
  • Sensor B may have internal failure or degraded output causing a high-voltage reading or a stuck-high condition.
• Wiring harness or connector problems on CMP B Bank 1 signal circuit: 25-35%
  • Damaged insulation, chafed wires, shorts to Vcc or ground, corroded connectors, or loose pins can pull the signal high or create a false high reading.
• ECU input circuit fault (PCM/ECU): 5-15%
  • An intermittent PCM input fault can interpret a normal signal as high or can fail to clamp the line properly.
• Intermittent mechanical timing issues or cam-phasing anomalies manifesting as sensor misreadings: 5-10%
  • In some engines, timing chain/belt slippage or valve timing issues can produce abnormal cam-sensor readings under certain conditions.
• Other related sensor or HV electrical issues (e.g., 5V reference issues affecting CMP sensing): 5-10%
  • If the 5V reference feed or ground to the CMP network is compromised, a "high input" reading could occur indirectly.

Important Notes

What to inspect and how to test (step-by-step diagnostic flow)

1) Confirm the DTC and gather data

• Verify P0368 is present in the PCM trouble codes and note any related CMP-related codes (P0360-P0369 family for CMP A/B banks). Review freeze-frame data for engine RPM, load, coolant temperature, and sensor signal values at the time the fault was logged.
• If available, record the CMP B signal voltage in live data and observe how it behaves as you rotate the engine (or when cranking).

2) Visual inspection of hardware

• Inspect the CMP B sensor and its mounting for damage, oil leaks, or contamination.
• Check the wiring harness, connectors, and pins for corrosion, bent pins, loose connectors, or damaged insulation on the Bank 1 CMP B circuit.
• Inspect the connector seals and ensure a solid, clean electrical connection.

3) Electrical checks (safety first)

• With the ignition ON (engine OFF, as applicable), verify the CMP B circuit voltage using back-probing:
  • Confirm proper reference voltage (often a 5V reference on CMP sensor circuits; refer to the service manual for your vehicle) and ground integrity.
  • Check for a stable reference and a clean signal path to the PCM.
• Check for shorts:
  • Short to 5V or short to GND on the CMP B signal wire can cause a circuit high input reading; verify continuity to the sensor and to the PCM input.
  • Check for accidental cross-overs with other nearby wires or harness damage that could inject voltage into the CMP B line.
• Verify ground integrity:
  • A poor or intermittent ground on the CMP B circuit can manifest as anomalous readings; ensure a solid ground path from the sensor back to the PCM chassis/engine ground.

4) Sensor-specific testing (CMP B)

• Compare CMP B signal with a known-good sensor if available:
  • Swap or bench-test with a known-good CMP B sensor to determine if the issue follows the sensor.
  • If swapping is not feasible, test the sensor in-place by measuring its output while manually rotating the cam (or using a controlled method to rotate the engine, where safe and permissible). The output should vary with cam position and not remain stuck at a high level.
• If the CMP B sensor is Hall-effect based or produces a digital-style signal, observe whether the waveform is clean and transitions rapidly with cam movement. A constant high or erratic waveform supports a sensor failure or wiring fault.

5) ECU/PCM checks

• If the sensor and wiring check out, but the fault persists, an ECU input fault should be considered:
  • Check for input noise or abnormal PCM behavior; review any updated ECU software or service bulletins for the specific vehicle.
  • In many cases,ECU-related faults are less common than sensor or harness faults for P0368, but they must be considered if all physical tests pass.

6) Mechanical timing context (when relevant)

• For engines with variable cam timing or dual cam sensors, verify timing alignment and belt/chain integrity as per service information.
• If timing components are off, CMP readings may be erratic or mismatched, potentially contributing to sensor-read anomalies.

7) Post-repair verification

• Clear the DTCs and perform a road/test drive per the OEM-recommended procedure.
• Re-check for P0368 and any related CMP codes.
• Validate that live CMP B signals are within expected range and show proper voltage transitions with cam movement and engine RPM changes.
• Confirm there are no additional faults in related circuits and that the drivability symptoms have resolved.

Recommended diagnostic workflow (condensed)

• Step 1: Read DTCs and review freeze-frame data; note any related CMP codes (A/B).
• Step 2: Visually inspect CMP B sensor, its connector, and Bank 1 wiring for damage, corrosion, or loose connections.
• Step 3: Verify circuit integrity:
  • Check supply/reference voltage to CMP B circuit and establish a solid ground.
  • Check for shorts to power or ground on the CMP B signal line.
• Step 4: Test CMP B sensor output:
  • With a known-good sensor (if available) or by swapping the sensor, observe whether the high-input fault follows the sensor.
  • Use live data to confirm the CMP B signal voltage responds to cam movement and is not stuck high.
• Step 5: If the sensor and wiring test clean, inspect ECU input circuit or update software as recommended by the manufacturer.
• Step 6: Repair/replace faulty components, then re-test and clear codes.
• Step 7: Document findings and retest until the DTC is cleared and driveability is confirmed.

Repair Options

• Faulty CMP B Sensor Bank 1:
  • Replace CMP B sensor and reassemble with proper torque and connector seating.
• Wiring/connector fault in CMP B Bank 1 circuit:
  • Repair or replace damaged wiring; fix insulation, re-pin connectors as needed; apply appropriate weatherproof sealant or seals.
• ECU/PCM input fault:
  • If diagnosed as ECU fault, consult manufacturer service bulletin and PCM repair or replacement guidelines; software updates may be required.
• Mechanical timing concerns:
  • Correct any timing misalignment or timing-chain/belt issues if diagnosed as contributing to CMP readings.
• After any repair:
  • Clear codes, perform a test drive, and re-check for reoccurrence of P0368 and related CMP codes.

Notes

• Bank 1 refers to the side of the engine containing cylinder 1; CMP sensors are often designated A and B for multiple cam sensors in engines with variable timing or multiple camshafts.
• Circuit High Input indicates the PCM is seeing an abnormally high voltage on the CMP B signal line; causes typically center on sensor failure, wiring faults, or an ECU input fault.
• The sources used for this guide include:
  • Wikipedia: OBD-II sections on Diagnostic Trouble Codes and Powertrain Codes, which discuss how DTCs are used to monitor engine systems and that P0368 is part of the powertrain code family.
  • Open-source code definitions: The Portuguese-language listing describes the same fault in terms of CMP Sensor B Bank 1 High Input, aligning with P0368 (

Safety Considerations

• Always follow vehicle-specific service instructions and torque specifications when replacing sensors or connectors.
• Disconnect the battery or use proper PPE when working with electrical systems to avoid short circuits or shocks.
• When using test equipment (scope, DVOM), follow standard electrical safety practices, including proper probing and placing the engine in a safe state before starting diagnostics.

References (for further reading)

• Open-source code definition: Alto sinal de entrada sensor CMP - sensor B banco 1 (P0368) - CMP Sensor B Bank 1 High Input (descriptive code mapping). This aligns with the P0368 designation and describes the fault as a high input on CMP Sensor B Bank 1.

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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