MG ZS (Gen2) P0442 EVAP System Small Leak Detected

The P0442 EVAP System Small Leak Detected fault indicates that the engine control module (ECM) has identified a small leak within the Evaporative Emission Control (EVAP) system. The ECM performs leak integrity tests by sealing the EVAP system and monitoring fuel tank pressure changes. If it detects a pressure loss that exceeds the allowable limit for a small leak, it stores DTC P0442. This fault applies to the MG ZS Gen2 (ZS11 platform), introduced from 2024 onwards.

Symptoms

  • Check Engine Light illuminated
  • Fuel smell around the vehicle
  • Increased evaporative emissions
  • Failed emissions inspection
  • Slight reduction in fuel economy
  • No noticeable drivability concerns in most cases
  • Additional EVAP-related fault codes may be present

Possible Causes

  • Loose, damaged, or incorrectly fitted fuel filler cap
  • Small leak in an EVAP hose or vapour line
  • Cracked or damaged charcoal canister
  • Leaking EVAP purge valve
  • Faulty EVAP vent valve
  • Damaged fuel tank pressure sensor
  • Cracked fuel tank or filler neck
  • Split seals or O-rings within the EVAP system
  • Damaged wiring or electrical connectors
  • Engine control module (ECM) fault (rare)

Diagnosis

Diagnosis begins by confirming the stored fault code and reviewing freeze-frame data using a compatible diagnostic scan tool. The fuel filler cap should be inspected first, followed by a visual inspection of the EVAP hoses, charcoal canister, purge valve, and vent valve for signs of leaks or damage. A smoke machine is typically used to identify small leaks that cannot be detected visually, while live data from the fuel tank pressure sensor should be analysed to verify correct system operation. Manufacturer diagnostic procedures may also include leak testing of individual EVAP components and electrical testing of the purge and vent valves.

For vehicles operating in New Zealand, following OEM diagnostic procedures helps accurately locate small EVAP leaks without replacing serviceable components, reducing repair costs and diagnostic time.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, connector pinouts, EVAP system schematics, smoke testing procedures, fuel tank pressure sensor 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.