BMW E46 diesel glow plug fault
How do you test an E46 diesel glow plug?
1. Unplug the glow plug connector. 2. Measure the plug's resistance with a multimeter. A healthy plug's resistance is about 0.5-2 ohms. Infinite or very high resistance means a faulty plug. Measure the plugs removed, because a measurement made with the connector attached can read wrongly.
Where is the E46 diesel's glow control?
The M57 engine has a traditional glow relay. The newer M57N and M47N have an electronic control unit instead of the relay, which on the M57N is under the intake manifold. Its failure is common, and the fault code usually tells which plug is faulty.
Do all the glow plugs need replacing at once?
It is worth it, because the biggest job is removing the intake manifold. Replace the control unit at the same time if its condition is doubtful: a faulty control unit can destroy the new plugs, and vice versa. Poor-quality aftermarket plugs do not withstand the control unit's brief 12-volt spike as well as the originals.
How long does pre-glow last in cold weather?
On the M47N engine pre-glow is 0.5 seconds and extends to at most 2.7 seconds when the coolant is below -25 °C. The glow light in the instrument cluster only comes on below 0 °C. One glow cycle is enough, and it does not need to be repeated.