MG ZS (ZS11) P0108 MAP Sensor Circuit High Input

Diagnostic Trouble Code (DTC) P0108 indicates that the Engine Control Module (ECM) has detected that the Manifold Absolute Pressure (MAP) sensor signal voltage is higher than the expected operating range. The MAP sensor measures the pressure inside the intake manifold and continuously sends a voltage signal to the ECM. A high input voltage typically indicates that the ECM is interpreting the manifold pressure as excessively high (or engine vacuum as extremely low), which may be caused by an open circuit, a signal wire shorted to voltage, a faulty MAP sensor, or a wiring fault. When the ECM detects a MAP sensor voltage above its calibrated limit for a specified period, it stores DTC P0108 and illuminates the Check Engine Light.

Symptoms

• Check Engine Light illuminated
• Reduced engine performance
• Poor acceleration
• Engine hesitation
• Rough idle
• Hard starting
• Engine stalling
• Increased fuel consumption
• Reduced fuel economy
• Engine-related Diagnostic Trouble Codes (DTCs) stored

Possible Causes

• Faulty MAP sensor
• Open circuit in the MAP sensor signal wire
• MAP sensor signal wire shorted to the 5V reference or battery voltage
• Faulty 5-volt reference circuit
• Poor sensor ground connection
• Loose or corroded MAP sensor connector
• Damaged or chafed wiring harness
• Intake manifold or vacuum hose fault affecting sensor operation
• Water intrusion into the sensor connector
• Faulty Engine Control Module (ECM) (rare)

Diagnosis

Diagnosis begins by retrieving all stored Diagnostic Trouble Codes (DTCs) and freeze-frame data using an OEM-compatible diagnostic scan tool. The technician should review live data and compare the MAP sensor reading with the barometric pressure reading while the ignition is ON and the engine is OFF. A MAP sensor voltage that remains near the upper limit (typically close to 5 volts) or an unrealistically high manifold pressure reading indicates a sensor or circuit fault. Related DTCs such as P0106, P0107, P0113, P0172, or other 5-volt reference circuit faults should also be investigated, as they may indicate a shared electrical issue.

The MAP sensor, intake manifold, vacuum hose (where fitted), wiring harness, and electrical connectors should be inspected for damage, loose terminals, corrosion, oil contamination, or water intrusion. Electrical testing should include verifying the 5-volt reference supply, checking ground integrity, measuring the signal voltage, and testing circuit continuity according to OEM specifications. The technician should also inspect for damaged intake components or restrictions that could affect pressure readings. If the wiring and power supply circuits are within specification but the MAP sensor continues to output an abnormally high voltage, the MAP sensor should be replaced. If the fault remains after sensor replacement, the ECM input circuit should be tested before replacing the control module.

For vehicles operating in New Zealand, following OEM diagnostic procedures helps accurately distinguish among a faulty MAP sensor, an open circuit, damaged wiring, a poor electrical connection, an intake system fault, or an ECM failure before replacing expensive engine management components.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, ECU pinouts, connector views, MAP sensor circuit schematics, intake manifold pressure specifications, 5-volt reference circuit diagrams, live data reference values, oscilloscope testing procedures, and ECM diagnostic flowcharts. Access to the factory service manual significantly reduces diagnostic time and helps prevent unnecessary parts replacement.

Applicable Years

2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024

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