MG ZS

MG ZS (Gen2) P2138 Accelerator Pedal Position Correlation Fault

The P2138 Accelerator Pedal Position Correlation Fault indicates that the Engine Control Module (ECM) has detected an implausible correlation between the two accelerator pedal position (APP) sensor signals within the electronic accelerator pedal assembly. The MG ZS uses dual APP sensors as part of its electronic throttle control (drive-by-wire) system to provide redundant input for safety and precise throttle control. If the ECM detects that the two sensor signals differ beyond the manufacturer’s specified tolerance, it stores DTC P2138 and may limit engine performance to protect against unintended acceleration. This fault applies to the MG ZS Gen2 (ZS11 platform), introduced from 2024 onwards.

Symptoms

  • Check Engine Light illuminated
  • Reduced engine power
  • Vehicle enters limp-home mode
  • Poor throttle response
  • Hesitation during acceleration
  • Limited engine RPM
  • Slow or delayed acceleration
  • Cruise control disabled
  • Additional electronic throttle control fault codes may be present

Possible Causes

  • Faulty accelerator pedal position (APP) sensor assembly
  • Internal failure of Accelerator Pedal Position Sensor 1 or Sensor 2
  • Damaged accelerator pedal wiring harness
  • Loose, corroded, or damaged electrical connectors
  • Open circuit or short circuit in the APP sensor wiring
  • Poor sensor ground or reference voltage supply
  • Faulty electronic throttle control system
  • CAN Bus communication fault
  • Low battery or charging system voltage
  • Engine Control Module (ECM) fault (rare)

Diagnosis

Diagnosis begins by confirming the stored fault code and reviewing freeze-frame and live data using a compatible diagnostic scan tool. The outputs of Accelerator Pedal Position Sensor 1 and Sensor 2 should be monitored while slowly depressing and releasing the accelerator pedal to verify that both voltage signals increase and decrease smoothly while maintaining the correct correlation. The accelerator pedal assembly should be inspected for physical damage, while the wiring harness, connectors, reference voltage, ground circuits, and signal wiring should be tested for continuity, voltage drop, and short circuits. Manufacturer diagnostic procedures may also include testing the electronic throttle body, verifying throttle actuator operation, checking for ECM software updates, and confirming proper communication between the accelerator pedal assembly and the ECM.

For vehicles operating in New Zealand, following OEM diagnostic procedures helps accurately distinguish between a faulty accelerator pedal assembly, wiring fault, power supply issue, electronic throttle control problem, or ECM fault before replacing expensive electronic components.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, connector pinouts, accelerator pedal position sensor specifications, electronic throttle control diagnostics, reference voltage specifications, throttle relearn procedures, 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.