MG ZS (Gen2) Camshaft Position Sensor Fault

A Camshaft Position Sensor (CMP) Fault indicates that the Engine Control Module (ECM) has detected an incorrect, intermittent, or missing signal from the camshaft position sensor. The CMP sensor monitors the position and rotational speed of the camshaft, enabling the ECM to accurately control sequential fuel injection, ignition timing, variable valve timing (VVT), and synchronization with the crankshaft position sensor. If the camshaft position signal becomes unreliable or is lost, the engine may experience starting difficulties, poor performance, increased emissions, or enter a reduced-power operating mode. This fault applies to the MG ZS Gen2 (ZS11 platform), introduced from 2024 onwards.

Symptoms

  • Check Engine Light illuminated
  • Extended cranking before starting
  • Engine cranks but fails to start
  • Rough idle
  • Engine hesitation during acceleration
  • Poor acceleration
  • Reduced engine power
  • Engine misfires
  • Increased fuel consumption
  • Engine stalls intermittently
  • Reduced variable valve timing performance
  • Camshaft position sensor-related Diagnostic Trouble Codes (DTCs) stored

Possible Causes

  • Faulty camshaft position sensor
  • Damaged camshaft reluctor (trigger) wheel
  • Incorrect sensor air gap
  • Open circuit in the sensor wiring
  • Short circuit to ground or battery voltage
  • Loose, damaged, or corroded sensor connector
  • Damaged wiring harness
  • Poor sensor ground or reference voltage
  • Variable valve timing (VVT) system malfunction
  • Engine timing chain or timing belt misalignment
  • Low battery voltage affecting sensor operation
  • Faulty Engine Control Module (ECM) (rare)

Diagnosis

Diagnosis begins by confirming any stored Diagnostic Trouble Codes (DTCs) and reviewing freeze-frame and live data using a compatible diagnostic scan tool. The technician should verify that the ECM is receiving a valid camshaft position signal during engine cranking and normal operation. Live data should be examined for camshaft position, crankshaft synchronization, engine speed, and variable valve timing operation. The camshaft position sensor wiring, connector, reference voltage, power supply, and ground circuits should be inspected for corrosion, damaged terminals, loose connections, or wiring faults. Circuit continuity, voltage drop, and resistance tests should be performed to identify electrical faults. The camshaft reluctor wheel should be inspected for damage or contamination, while the engine timing chain or belt should be checked to ensure correct mechanical timing. An oscilloscope should be used to compare the camshaft position sensor waveform with the crankshaft position sensor waveform to confirm proper synchronization. Manufacturer diagnostic procedures may also include VVT actuator testing, camshaft timing verification, ECM input testing, and sensor signal analysis.

For vehicles operating in New Zealand, following OEM diagnostic procedures helps accurately distinguish between a faulty camshaft position sensor, damaged reluctor wheel, wiring fault, variable valve timing malfunction, engine timing issue, or ECM fault before replacing expensive engine management components.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, engine management schematics, connector pinouts, camshaft position sensor specifications, oscilloscope waveform references, crankshaft-to-camshaft synchronization procedures, variable valve timing diagnostics, timing chain inspection procedures, ECM input specifications, and system calibration information. Access to the factory service manual significantly reduces diagnostic time and helps prevent unnecessary parts replacement.

Applicable Years

2024, 2025, 2026, onwards

To order the correct OEM Service and Repair Manual for your MG ZS, submit your request using the form below, and our team will provide the ordering details.