A P0302 – Cylinder 2 Misfire Detected fault on the 2017 MG ZS indicates that the Engine Control Module (ECM) has detected incomplete or irregular combustion in cylinder 2. The ECM monitors crankshaft speed fluctuations to identify individual cylinder misfires, and when cylinder 2 repeatedly fails to combust correctly, it stores DTC P0302 and illuminates the Check Engine Light. If left unresolved, a cylinder misfire can reduce engine performance, increase fuel consumption and emissions, and potentially overheat or damage the catalytic converter. Accurate diagnosis is essential because the fault may be caused by ignition, fuel, mechanical, electrical, or engine management issues.

Symptoms

• Check Engine Light illuminated
• Flashing Check Engine Light during severe misfires
• Diagnostic Trouble Code (DTC) P0302 stored
• Rough or unstable idle
• Engine vibration or shaking
• Poor acceleration
• Reduced engine power
• Engine hesitation under load
• Hard starting
• Increased fuel consumption
• Engine stalling
• Increased exhaust emissions
• Fuel smell from the exhaust in severe cases

Possible Causes

The fault may be caused by a worn or faulty spark plug on cylinder 2, a defective ignition coil, damaged ignition coil wiring, injector circuit faults, a faulty or restricted fuel injector, low fuel pressure, vacuum leaks near cylinder 2, intake manifold gasket leaks, MAP sensor faults, throttle body faults, low engine compression, leaking valves, damaged piston rings, incorrect valve timing, crankshaft or camshaft position sensor faults, contaminated fuel, damaged wiring, poor electrical connections, Engine Control Module (ECM) faults, or CAN Bus communication issues affecting engine management.

Diagnosis

Diagnosis begins by confirming DTC P0302 with a professional diagnostic scan tool and reviewing freeze-frame data to identify the operating conditions when the misfire occurred. Live data should be analysed to assess fuel trim values, ignition timing, MAP sensor readings, and any additional Diagnostic Trouble Codes that may be contributing to the fault. If other cylinder-specific misfire codes or fuel system faults are present, they should be diagnosed as part of the overall repair.

A cylinder 2 misfire is not always caused by a faulty ignition component. Technicians typically inspect the cylinder 2 spark plug for wear or contamination and test the ignition coil by swapping it with another cylinder to determine whether the fault follows the coil. The cylinder 2 fuel injector should also be checked for correct electrical operation, injector pulse width, and fuel delivery. Wiring, connector condition, battery voltage, and ground integrity should be verified before replacing any components.

If the ignition and fuel systems test correctly, further diagnosis should include compression testing, cylinder leak-down testing, intake manifold inspection for vacuum leaks, valve timing verification, crankshaft and camshaft position sensor testing, and evaluation of the Engine Control Module and associated communication circuits. Access to OEM wiring diagrams, connector pinouts, component locations, circuit descriptions, diagnostic flowcharts, and manufacturer troubleshooting procedures is essential for accurate fault isolation. Following the OEM diagnostic workflow helps identify the underlying cause efficiently while preventing unnecessary replacement of ignition, fuel, or engine management components.

Recommended Resources

OEM Service and Repair Manual

The OEM Service and Repair Manual is the most reliable resource for diagnosing and repairing a P0302 cylinder 2 misfire fault. It typically includes:

• Diagnostic procedures specific to DTC P0302
• OEM misfire diagnostic flowcharts
• Engine management wiring diagrams and circuit descriptions
• Ignition coil and spark plug testing procedures
• Fuel injector diagnostic procedures
• Compression and leak-down testing specifications
• Connector pinout information
• Component locations and removal procedures
• Repair specifications and electrical testing procedures

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