MG ZS (Gen2) P0300 Random Misfire Fault

The P0300 Random Misfire Fault indicates that the engine control module (ECM) has detected multiple or randomly occurring engine misfires that cannot be attributed to a single cylinder. This fault affects the engine management, ignition, and fuel injection systems and is detected by monitoring crankshaft speed variations that indicate incomplete or inconsistent combustion events. It applies to the MG ZS Gen2 (ZS11 platform), introduced from 2024 onwards.

Symptoms

  • Check Engine Light illuminated
  • Flashing Check Engine Light during severe misfires
  • Rough or unstable idle
  • Engine hesitation
  • Reduced engine power
  • Poor acceleration
  • Hard starting
  • Increased fuel consumption
  • Engine vibration
  • Higher exhaust emissions

Possible Causes

  • Worn or faulty spark plugs
  • Faulty ignition coils
  • Faulty fuel injectors
  • Low fuel pressure
  • Vacuum leak in the intake system
  • Faulty mass airflow (MAF) sensor
  • Faulty crankshaft or camshaft position sensor
  • Low engine compression
  • Timing-related issues
  • Contaminated or poor-quality fuel
  • Wiring or connector faults
  • Engine control module (ECM) fault (rare)

Diagnosis

Diagnosis begins by confirming the stored fault code and reviewing freeze-frame data and cylinder misfire counters using a compatible diagnostic scan tool. The ignition system, fuel delivery system, intake system, and engine mechanical condition should then be inspected to identify the source of the intermittent or multiple-cylinder misfires. Manufacturer diagnostic procedures may also include ignition waveform analysis, fuel pressure testing, compression testing, and checking crankshaft and camshaft sensor signals to isolate the root cause.

Random misfire faults are frequently encountered in New Zealand vehicles exposed to varying fuel quality, stop-start urban driving, and extended highway operation, making accurate diagnosis essential before replacing components.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, connector pinouts, specifications, ignition system data, fuel pressure 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.