A P0335 – Crankshaft Position Sensor Circuit Fault on the 2018 MG ZS indicates that the Engine Control Module (ECM) has detected an invalid, missing, or intermittent signal from the Crankshaft Position (CKP) Sensor circuit. The CKP sensor is one of the most critical engine management sensors, providing the ECM with precise information about crankshaft speed and position. This data is used to control ignition timing, fuel injection, variable valve timing, and engine synchronisation.

When the ECM cannot reliably receive or interpret the CKP signal, it stores Diagnostic Trouble Code P0335 and illuminates the Check Engine Light. Depending on the severity of the fault, the engine may experience hard starting, stalling, poor performance, or a complete no-start condition. Common causes include a faulty CKP sensor, damaged wiring, connector faults, reluctor wheel damage, timing component issues, or an ECM-related fault.

Symptoms

• Check Engine Light illuminated
• Diagnostic Trouble Code (DTC) P0335 stored
• Engine cranks but will not start
• Intermittent no-start condition
• Engine stalls while driving
• Hard starting
• Rough engine idle
• Engine misfires
• Reduced engine performance
• Additional crankshaft or camshaft-related Diagnostic Trouble Codes may also be present

Possible Causes

The fault may be caused by a defective crankshaft position sensor, damaged reluctor wheel, excessive sensor air gap, open or short circuit in the CKP sensor wiring, loose or corroded electrical connectors, poor ground connections, damaged wiring harnesses, timing chain wear causing synchronisation errors, faulty camshaft position sensor, Engine Control Module (ECM) faults, blown fuses affecting the sensor circuit, low reference voltage, or CAN Bus communication issues affecting engine management. Circuit faults and damaged wiring are among the most common causes of DTC P0335.

Diagnosis

Diagnosis begins by connecting a professional diagnostic scan tool to retrieve DTC P0335 together with any related engine management, crankshaft position, camshaft position, or synchronisation Diagnostic Trouble Codes. Freeze-frame data and live data should be analysed to monitor engine speed during cranking, crankshaft position sensor signal status, camshaft synchronisation, battery voltage, and communication between the Engine Control Module and other vehicle control modules. Any accompanying camshaft position or timing-related Diagnostic Trouble Codes should be diagnosed before replacing components.

A P0335 fault is not always caused by a failed crankshaft position sensor. Technicians typically inspect the CKP sensor and reluctor wheel for physical damage, verify the sensor air gap, and test the sensor power supply, ground, and signal circuits before replacing components. Wiring harnesses, electrical connectors, battery voltage, engine ground circuits, and timing chain condition should also be inspected. Where necessary, an oscilloscope should be used to compare the crankshaft position sensor waveform with manufacturer specifications to identify intermittent signal loss or synchronisation faults.

If the crankshaft position sensor and associated circuits operate within specification, further diagnosis should include evaluation of the Engine Control Module, engine synchronisation, timing components, and the CAN Bus communication network. Access to OEM wiring diagrams, connector pinouts, CKP circuit descriptions, oscilloscope waveform specifications, component locations, timing inspection procedures, and manufacturer diagnostic flowcharts is essential for accurate fault isolation. Following the OEM troubleshooting workflow helps identify the underlying cause efficiently while avoiding unnecessary replacement of sensors, wiring harnesses, timing components, or electronic control modules.

Recommended Resources

OEM Service and Repair Manual

The OEM Service and Repair Manual is the most reliable resource for diagnosing and repairing a P0335 Crankshaft Position Sensor Circuit Fault. It typically includes:

• Diagnostic procedures specific to DTC P0335
• Engine management wiring diagrams and circuit descriptions
• Crankshaft Position (CKP) sensor testing procedures
• CKP sensor waveform and signal specifications
• Reluctor wheel inspection procedures
• Timing chain inspection and synchronisation procedures
• Camshaft and crankshaft correlation testing
• Connector pinout information
• Component locations and removal procedures
• OEM troubleshooting workflows
• Repair specifications and electrical testing procedures

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