An Intermittent No Start Condition on the 2017 MG ZS occurs when the engine occasionally fails to start despite functioning normally at other times. The fault can be particularly challenging to diagnose because it may not be present when the vehicle is inspected.

The engine management system relies on consistent communication between the Engine Control Module (ECM), Body Control Module (BCM), immobilizer, fuel delivery system, ignition system, and various sensors to initiate combustion. An intermittent failure in any of these systems may prevent the engine from starting without leaving an obvious permanent fault.

Environmental conditions, temperature changes, vibration, or poor electrical connections can also contribute to an intermittent no-start condition. Accurate diagnosis using OEM procedures is essential to identify the underlying cause without unnecessary replacement of components.

Symptoms

• Engine intermittently cranks but does not start
• Vehicle starts normally after several attempts
• No-start condition occurs randomly
• Extended cranking before the engine starts
• Immobilizer warning light illuminates intermittently
• Check Engine Light may illuminate
• No fuel pump priming sound during some start attempts
• Intermittent loss of spark or injector operation
• Multiple warning lights may appear temporarily
• Diagnostic Trouble Codes may be intermittent or absent

Possible Causes

The fault may be caused by an intermittent crankshaft position sensor, faulty camshaft position sensor, failing fuel pump, intermittent fuel pump relay, low fuel pressure, worn ignition coils, failing spark plugs, immobilizer communication faults, defective key transponder, weak battery, poor battery terminals, damaged ground straps, faulty starter relay, loose or corroded electrical connectors, damaged wiring harnesses, Engine Control Module (ECM) faults, Body Control Module (BCM) faults, faulty Engine Coolant Temperature (ECT) sensor, failing ignition switch, or CAN Bus communication issues. Heat-related electronic failures and intermittent electrical connections are common contributors to this type of fault.

Diagnosis

Diagnosis begins by connecting a professional diagnostic scan tool capable of communicating with all vehicle control modules and retrieving both stored and pending Diagnostic Trouble Codes. Freeze-frame data and live data should be analysed to determine whether the ECM receives crankshaft and camshaft position signals, immobilizer authorization, fuel pressure information (where available), engine coolant temperature, battery voltage, and ignition switch status during a no-start event. If possible, diagnosis should be performed while the fault is actively occurring, as intermittent faults may not leave permanent evidence once the engine starts successfully.

An intermittent no-start condition is not always caused by a failed fuel pump or starter motor. Technicians typically verify battery condition, inspect battery terminals and engine ground connections, test the fuel pump relay, confirm fuel pressure, verify ignition spark, and monitor injector pulse before replacing components. Wiring harnesses, connectors, and control module power supplies should be inspected for loose terminals, corrosion, damaged insulation, or signs of heat-related failure. Components known to fail intermittently, such as crankshaft position sensors, ignition relays, or ignition switches, should be evaluated using live data, electrical testing, or an oscilloscope where appropriate.

If the fuel, ignition, and primary electrical systems operate within specification, further diagnosis should include the immobilizer system, Engine Control Module, Body Control Module, power distribution circuits, and the CAN Bus communication network. Access to OEM wiring diagrams, connector pinouts, component locations, immobilizer programming procedures, circuit descriptions, and manufacturer diagnostic flowcharts is essential for accurate fault isolation. Following the OEM troubleshooting workflow helps identify intermittent failures efficiently while avoiding unnecessary replacement of sensors, relays, fuel system 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 an intermittent no-start condition. It typically includes:

• Comprehensive intermittent no-start diagnostic procedures
• Engine management wiring diagrams and circuit descriptions
• Fuel system and fuel pressure testing procedures
• Ignition system diagnostic procedures
• Crankshaft and camshaft position sensor testing
• Immobilizer and key programming procedures
• Battery, charging, and ground circuit diagnostics
• Connector pinout information
• Component locations and removal procedures
• OEM troubleshooting workflows
• Repair specifications and electrical testing procedures

To order the correct OEM Service and Repair Manual for your 2017 MG ZS, submit your request using the form below and our team will provide the ordering details.