When checking, the battery must be charged (minimum battery voltage 11.5V), the engine control unit and the fuse protecting the glow plug supply circuit must be in good condition.
1. With the ignition off, disconnect the wiring harness from the coolant temperature sensor, which simulates a cold engine.
2. Disconnect the tips from the glow plugs.
3. Connect a voltmeter between the tip of any spark plug and «weight» engine.
4. Turn on the ignition, the voltmeter should show a voltage close to the battery voltage for about 20 seconds. If the voltmeter shows 0, there is an open or short circuit in the power circuit.