• posted by Craig Murray

A P0128 – Coolant Temperature Below Thermostat Regulating Temperature fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has determined that the engine coolant has failed to reach the manufacturer’s specified operating temperature within the expected time after engine start-up.

The ECM continuously monitors engine warm-up using data from the Engine Coolant Temperature (ECT) sensor, intake air temperature sensor, engine run time, vehicle speed, and engine load.

When the coolant temperature remains below the calibrated threshold for longer than expected, the ECM stores Diagnostic Trouble Code P0128 and illuminates the Check Engine Light.

In most cases, this condition is caused by a thermostat that is stuck partially or fully open, allowing coolant to circulate through the radiator before the engine reaches its normal operating temperature.

Operating the engine below its designed temperature can increase fuel consumption, delay closed-loop fuel control, increase exhaust emissions, reduce cabin heater performance, and accelerate engine wear.

• posted by Craig Murray

A P0123 – Throttle Position Sensor (TPS) Circuit High Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected a throttle position sensor signal voltage that is higher than the manufacturer’s specified operating range.

The MG ZS utilizes an electronic throttle control (drive-by-wire) system in which the throttle position sensor continuously reports the throttle plate angle to the ECM. This information is essential for controlling fuel injection, ignition timing, idle speed, torque management, transmission shift strategy, emissions systems, and electronic throttle operation.

Under normal operating conditions, the TPS signal rises smoothly from approximately 0.5 volts at closed throttle to about 4.5 volts at wide-open throttle.

When the ECM detects a signal voltage exceeding the calibrated threshold—typically above 4.8 volts—it stores Diagnostic Trouble Code P0123, illuminates the Check Engine Light, and may place the vehicle into reduced power (limp-home) mode to protect the electronic throttle system. Common causes include a short to the 5-volt reference, an open sensor ground, a faulty throttle position sensor, damaged wiring, or an internal electronic throttle body fault.

• posted by Craig Murray

A P0122 – Throttle Position Sensor (TPS) Circuit Low Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected a throttle position sensor signal voltage that is lower than the manufacturer’s specified operating range.

The MG ZS uses an electronic throttle control (drive-by-wire) system in which the throttle position sensor continuously reports the throttle plate angle to the ECM. This information is used to regulate fuel injection, ignition timing, idle speed, torque management, transmission shift strategy, and emissions control.

When the TPS signal falls below the expected threshold, the ECM interprets the throttle position as implausibly low or detects a circuit fault.

As a result, Diagnostic Trouble Code P0122 is stored, the Check Engine Light is illuminated, and the vehicle may enter reduced power (limp-home) mode to protect the electronic throttle system. Common causes include a short-to-ground in the TPS signal circuit, a faulty throttle position sensor, damaged wiring, poor electrical connections, or an internal electronic throttle body failure.

• posted by Craig Murray

A P0121 – Throttle Position Sensor (TPS) Range/Performance Fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected that the signal from the throttle position sensor is outside the expected operating range or is not plausible when compared with other engine operating parameters.

On the MG ZS electronic throttle control (drive-by-wire) system, the throttle position sensor continuously reports the throttle plate angle to the ECM, allowing it to accurately control fuel injection, ignition timing, idle speed, torque management, and electronic throttle operation.

The ECM continuously compares the TPS signal with the Accelerator Pedal Position (APP) sensor, Manifold Absolute Pressure (MAP) sensor, Mass Air Flow (MAF) sensor, and engine speed to verify signal accuracy. If the TPS voltage is erratic, inconsistent, or does not correlate with these inputs, Diagnostic Trouble Code P0121 is stored and the Check Engine Light is illuminated.

The vehicle may also enter reduced power (limp-home) mode to protect the engine and electronic throttle system. Common causes include a faulty throttle position sensor, carbon buildup inside the throttle body, damaged wiring, poor electrical connections, or an internal electronic throttle body fault.

• posted by Craig Murray

A P0118 – Engine Coolant Temperature (ECT) Sensor Circuit High Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected a voltage signal from the Engine Coolant Temperature sensor that is higher than the manufacturer’s calibrated operating range.

The ECT sensor is a negative temperature coefficient (NTC) thermistor that monitors engine coolant temperature and provides the ECM with critical information for fuel injection, ignition timing, cold-start enrichment, idle speed control, radiator cooling fan operation, and emissions management.

Because the ECT sensor’s resistance decreases as coolant temperature rises, a high input voltage is interpreted by the ECM as an implausibly low coolant temperature, often around -40°C (-40°F). When this condition is detected, the ECM stores Diagnostic Trouble Code P0118 and illuminates the Check Engine Light. Common causes include an open circuit, disconnected sensor, damaged wiring, poor electrical connections, a failed ECT sensor, or an internal ECM fault.

• posted by Craig Murray

A P0117 – Engine Coolant Temperature (ECT) Sensor Circuit Low Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected a voltage signal from the Engine Coolant Temperature sensor that is lower than the manufacturer’s specified operating range.

The ECT sensor is a negative temperature coefficient (NTC) thermistor that monitors engine coolant temperature and provides the ECM with essential data for controlling fuel injection, ignition timing, cold-start enrichment, idle speed, radiator fan operation, and emissions systems.

A low input voltage is typically interpreted by the ECM as an excessively high engine coolant temperature, even when the engine may not actually be overheating. When this condition is detected, the ECM stores Diagnostic Trouble Code P0117 and illuminates the Check Engine Light.

Common causes include a short-to-ground in the sensor circuit, a failed ECT sensor, damaged wiring, connector faults, low coolant level, or an internal ECM malfunction.

• posted by Craig Murray

A P0113 – Intake Air Temperature (IAT) Sensor Circuit High Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected an intake air temperature sensor signal voltage that is higher than the manufacturer’s specified operating range.

The IAT sensor is a negative temperature coefficient (NTC) thermistor that measures the temperature of the incoming air, allowing the ECM to calculate air density and optimize fuel injection, ignition timing, engine load, and emissions control. A high input voltage is typically interpreted as an unrealistically low intake air temperature, often around -40°C (-40°F), causing the ECM to enrich the air-fuel mixture and adjust engine operating parameters.

When this condition is detected, the ECM stores Diagnostic Trouble Code P0113 and illuminates the Check Engine Light. Common causes include an open circuit, disconnected sensor, damaged wiring, poor electrical connections, or a faulty IAT sensor.

• posted by Craig Murray

A P0112 – Intake Air Temperature (IAT) Sensor Circuit Low Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected an intake air temperature sensor signal voltage that is lower than the manufacturer’s calibrated operating range.

The IAT sensor is a thermistor that measures the temperature of the incoming air, enabling the ECM to adjust fuel injection, ignition timing, engine load calculations, and emissions control.

A low input voltage is typically interpreted by the ECM as an unrealistically high intake air temperature, causing it to alter fuel delivery and ignition strategies.

When this condition is detected, the ECM stores Diagnostic Trouble Code P0112 and illuminates the Check Engine Light. Common causes include a short to ground, damaged wiring, a faulty IAT sensor, connector corrosion, or an internal ECM fault.

• posted by Craig Murray

A P0106 – Manifold Absolute Pressure (MAP) Sensor Range/Performance Fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected that the MAP sensor signal is outside the expected operating range or is inconsistent with other engine operating parameters, such as throttle position, engine speed, intake air temperature, and Mass Air Flow (where applicable).

The MAP sensor measures the absolute pressure inside the intake manifold, allowing the ECM to determine engine load and accurately calculate fuel injection, ignition timing, and Variable Valve Timing (VVT) operation.

When the sensor reading becomes implausible or fails the ECM’s rationality checks, Diagnostic Trouble Code P0106 is stored and the Check Engine Light is illuminated. Common causes include a faulty MAP sensor, vacuum leaks, intake restrictions, wiring faults, or engine mechanical issues affecting manifold pressure.

• posted by Craig Murray

A P0103 – Mass Air Flow (MAF) Sensor Circuit High Input fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected a Mass Air Flow sensor signal that is higher than the manufacturer’s expected operating range. The MAF sensor measures the amount of air entering the engine and sends a voltage or frequency signal to the ECM, which uses this information to calculate fuel injection, ignition timing, engine load, and Variable Valve Timing operation.

When the ECM receives an abnormally high input signal that does not correspond to actual engine operating conditions, it stores Diagnostic Trouble Code P0103 and illuminates the Check Engine Light. Depending on the severity of the fault, the ECM may activate a fail-safe strategy using substitute airflow values, resulting in reduced engine performance and increased fuel consumption. Common causes include a faulty MAF sensor, wiring faults, connector problems, or ECM-related issues.