Glow Plug Control Module: Description and Operation

Position in model 140 in control module box






Position in models 202 and 210
At front left behind the headlamp






Design

Task
Actuating the pencil-type glow plugs.

Function
With ignition ON the engine control module transmits a signal to the glow output stage (N14/2). If no data transfer with the engine control module takes place, glow plug heating is aborted after 2 seconds. The glow output stage constantly signals the current operating state (glow plug heating "ON" or "OFF") and system faults. The following faults are detected and transmitted to the engine control module:
- Open circuit of one or more glow plugs
- Short circuit in glow plug circuit
- Relay fault

Open circuit at glow plug (R9)
If the engine control module detects a corresponding fault, the fault is then stored and indicated at the earliest from the moment the engine is running by the preglow indicator lamp (A1e16) coming on for about 1 minute. The fault is stored in the engine control module.

Short circuit or glow output stage faulty
If the engine control module detects a corresponding fault, it is stored and immediately indicated by the preglow indicator lamp (A1e16) coming on. If the fault is no longer current, the indication is switched off immediately but the fault is stored in the engine control module. If the fault is constantly current, the preglow indictor lamp (A1e16) remains on until the ignition is switched off.

Fault in communication
If the engine control module detects a corresponding fault (e.g. open circuit in wiring), the fault is stored and immediately indicated by the preglow indictor lamp (A1e16) coming on. If the fault is no longer current, the indication is switched off immediately but the fault is stored in the engine control module.

If the fault is constantly current, the preglow indicator lamp (A1e16) remains on until the ignition is switched off.