Control Unit

On CIS Motronic and CIS Digital Control (DC) system, the control unit is referred to as the Electronic Control Unit (ECU). On the CIS-E III system, 2 interfacing computers are used and are referred to as the Ignition Control Unit (ICU), and Fuel Injection Control Unit (FICU). When a knock sensor is used in the system the control unit is referred to as a Knock Sensor Control Unit (KSCU).

In operation, the control unit receives signals from the air sensor potentiometer, oxygen sensor, coolant temperature sensor, throttle valve switches,O2 sensor and other sensors specific to the individual system. Using this data the control unit varies air fuel mixture and ignition timing to maintain optimum performance, fuel economy and emission standards.

Fig 1: CIS Digital Control (DC) System Components

Courtesy of AUDI OF AMERICA, INC.

Fig 2: CIS-E System Components

Courtesy of AUDI OF AMERICA, INC.

Fig 3: CIS Motronic System Components

Courtesy of AUDI OF AMERICA, INC.

NOTE: For ease of understanding, components are grouped into 2 categories. The first category, INPUT DEVICES, is components which control or produce voltage signals that are monitored by the ECU. The second category, OUTPUT SIGNALS, are components that are controlled by the ECU (this is usually accomplished by the ECU grounding individual circuits).