P0380 / P0670 fault codes - Glow plugs
P0380: Glow plug/heater circuit A - Malfunction (2.0 HDi engine)
In this example, the fault code does not turn on the check engine light. It indicates a fault in the glow plug circuit, without identifying the exact cause. The most likely cause is a faulty glow plug. Glow plugs contain a heating element that warms the combustion chamber to help the engine start (pre-glow) and continues heating during the first seconds of engine operation (post-glow). Checking the glow plugs is an important maintenance step that can help reduce fuel consumption.
The glow plugs can be tested individually without necessarily removing them (Fig. 2-1). Disconnect the connector or power supply wires, then test each plug with a multimeter set to measure resistance. Their resistance is generally around 0.7 ohm. Most multimeters are not accurate enough to measure such a low resistance precisely and may display 1 or 2 ohms. This can confirm continuity, but is not a complete performance test. A failed heating element may show an open circuit (Fig. 2-2, infinite resistance).
P0670: Glow plug control module - Circuit malfunction (dCi engine)
Renault/Nissan dCi engines may return a different fault code. Like P0380, it does not identify the exact cause. Follow the same procedure and test the glow plugs first. If they are working, the next likely cause is the relay control module supplying them during pre-glow and post-glow.
With a multimeter set to measure voltage, check the voltage across the glow plug terminals during pre-glow.
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