Torque Specifications
| Description | Nm | lb-ft |
| glow plugs | 10 | 7 |
Description and principle of operation
| Pos. | spare part no | Name |
| 1 | - | glow plugs |
| 2 | - | Control lamp for glow plugs |
| 3 | - | BJB |
Glow plugs are installed on the intake side of each cylinder; they serve to warm up the combustion chambers before and during cranking. This facilitates cold starts, reduces emissions and reduces engine noise when the engine is idling cold.
The wiring harness on each row of glow plugs is connected to a separate relay and fusible link in the BJB (battery electrical junction box). Each glow plug is grounded through a mounting on the cylinder head. The glow plug relay is controlled by the ECM, which also controls the activation of the glow plug warning light on the instrument panel.
Each glow plug is a tubular heating element with a spiral filament that is encased in powdered magnesium oxide. A heating coil is located in the tip of the tubular heating element. Behind the heating coil is a serially connected control coil. The control coil regulates the current supplied to the heating coil, providing overheating protection.
Job
There are three phases of glow plug operation: Pre-heating, cranking heating and post-heating. The ECM determines the warm-up time based on the ECT signal (engine coolant temperature). The lower the engine coolant temperature, the longer the warm-up time.
When the ignition switch is turned to position II, the ECM calculates any required warm-up time and, if warm-up is required, activates the glow plug relay in the BJB. When there is a need for preheating, the ECM sends a high speed CAN·message to the instrument cluster to request the glow plug warning light to come on. The glow plug warning light remains on until the end of the first phase or until the key is turned to the crank position, whichever comes first. If necessary, the ECM leaves the glow plug relay on both during cranking and for a certain amount of time after the engine is started.
The ECM monitors the power and control circuit of the glow plug relay for correct operation, electrical continuity, short circuit, or open circuit. When a malfunction is detected, the ECM records the appropriate DTC and keeps the glow plug warning lamp on at all times when the ignition switch is in position II.
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