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What to Do When the Dashboard Displays 'Preheat Malfunction'. Which Glow Plug to Replace.

Model: (Various brands) Various
Part: Glow plugs

Learn how to identify which glow plug to replace when the dashboard displays 'Preheat Malfunction'. First, disconnect the battery, then remove the coil to access the cables underneath. Remove the connector from the fuel filter to create more space; this will give you access to the glow plug connectors. You will need to remove one clip. Each wire corresponds to a glow plug, so follow the wire colours to the plug. To test them, strip a common electrical wire from both ends, reconnect the battery, and test the glow plugs: be careful as connecting the wire to the battery poses a shock risk. If you see a spark, the plug works. If there are no sparks, the plug needs replacing. This procedure can be used on any diesel engine, but the coil's position may vary from model to model, as may the removal method.

Updated on 10 July 2026 by ScegliAuto

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