P0380: Glow plug/Heater, circuit A - malfunction (2.0 HDi engine)
This fault code does not light a lamp on the dashboard. It indicates a problem in the preheating circuit. This generic fault code does not specify the exact cause of the problem. The probable cause is a malfunction of the glow plugs themselves. They operate on a simple principle. They are comprised of a heating resistance which, when powered, will heat up the combustion chamber during the first seconds of engine operation to facilitate ignition (Pre-heating) and accelerate temperature rise in it (Post-heating).
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They can be tested one by one, without necessarily removing them (Fig 2-1). Remove the connector or power wires and test them using a multimeter set to ohmmeter. They usually have a resistance of the order of 0.7 Ohm. Most multimeters are not accurate enough to measure this type of resistance. The display will show a resistance of 1 or 2 Ohm. This is enough to tell if the plug is working. Malfunctioning plugs have cut internal resistance (Fig 2-2 infinite resistance).