MG ZS (Gen2) Crankshaft Position Sensor Fault

A Crankshaft Position Sensor (CKP) Fault indicates that the Engine Control Module (ECM) is receiving an incorrect, intermittent, or missing signal from the crankshaft position sensor. The CKP sensor monitors the crankshaft’s rotational speed and position, allowing the ECM to accurately control ignition timing, fuel injection timing, variable valve timing, and engine synchronization. If the crankshaft position signal becomes unreliable or is lost, the ECM may be unable to determine engine position, resulting in hard starting, engine stalling, or a complete no-start condition. This fault applies to the MG ZS Gen2 (ZS11 platform), introduced from 2024 onwards.

Symptoms

  • Check Engine Light illuminated
  • Engine cranks but fails to start
  • Extended cranking before starting
  • Engine stalls unexpectedly
  • Intermittent stalling while driving
  • Rough idle
  • Poor acceleration
  • Engine hesitation
  • Misfires
  • Reduced engine performance
  • Tachometer may not register during cranking
  • Crankshaft position sensor-related Diagnostic Trouble Codes (DTCs) stored

Possible Causes

  • Faulty crankshaft position sensor
  • Damaged crankshaft 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
  • Engine timing component damage affecting sensor readings
  • Excessive metal debris on the magnetic sensor tip
  • Low battery voltage affecting signal quality
  • 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. During engine cranking, the technician should verify whether the ECM is receiving a valid engine speed (RPM) signal from the crankshaft position sensor. The sensor wiring, connector, power supply, reference voltage, and ground circuits should be inspected for damage, corrosion, loose terminals, or poor electrical connections. Circuit continuity, voltage drop, and resistance tests should be performed to identify opens, shorts, or excessive resistance. The crankshaft reluctor wheel should be inspected for damaged, missing, or contaminated teeth, and the sensor air gap should be verified against manufacturer specifications. An oscilloscope is often used to evaluate the crankshaft position sensor waveform and confirm signal integrity during engine cranking and operation. Manufacturer diagnostic procedures may also include synchronization testing between the crankshaft and camshaft position sensors, ECM input verification, and wiring integrity tests.

For vehicles operating in New Zealand, following OEM diagnostic procedures helps accurately distinguish between a faulty crankshaft position sensor, damaged reluctor wheel, wiring fault, timing-related issue, poor electrical connection, 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, crankshaft position sensor specifications, reluctor wheel inspection procedures, oscilloscope waveform references, synchronization testing 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.