Injection Electronics

CIRCUIT OPERATION

- The Motronic Control Unit uses signals from engine sensors and switches to regulate spark, fuel injection, and exhaust emissions.

- The Control Unit receives input signals from the following components:

- Cylinder Identification Sensor
- Engine Speed Sensor
- Oxygen Sensor
- Coolant Temperature Sensor
- On-Board Computer Relay Box
- Ignition Switch
- Automatic Transmission Range Switch
- Throttle Switch

- The Motronic Control Unit determines engine speed and piston position from the pulses transmitted by the Engine Speed Sensor.
- The Oxygen Sensor supplies a varying voltage to the Control Unit. The voltage varies as the air/fuel ratio changes from lean to rich.
- The Coolant Temperature Sensor is a NTC thermistor. The resistance value of the sensor decreases as the temperature of the engine coolant increases.
- The Throttle Switch signals the Control Unit when the throttle is opened or closed.
- When the On-Board Computer or Fault Code System is activated, the On-Board Computer Relay Box interrupts power to the Motronic Control Unit. The ignition and injection signals are disabled and the car will not start.

- The Motronic Control Unit controls the following outputs:
- Main Relay
- Fuel Pump Relay
- Ignition Coil
- Evaporator Purge Valve
- Idle Speed Actuator
- Fuel Injectors
- Engine speed signal
- Oxygen Sensor Heater Relay

- The Motronic Control Unit determines the ignition timing, dwell angles, and amount of fuel to be injected from the input sensors and switches.