Federal Models

The CIS-E (Continuous Injection System / Electric) system precisely controls fuel injection quantity under varying operating conditions. The CIS-E control unit evaluates information provided by various sensors concerning engine operating conditions, and from the information received generates a control signal for the electro-hydraulic actuator. Input signals include:

^ Overvoltage protection relay B+
^ Coolant temperature sensor
^ EGR temperature sensor (California Only)
^ Electronic ignition control unit (EZL)
^ Air flow sensor position indicator
^ Throttle valve switch (idle and full load)
^ Microswitch
^ Oxygen sensor
^ Intake air temperature sensor
^ Transmission range selector
^ Vehicle speed sensor

The electro-hydraulic actuator regulates pressure in the lower chambers of the CIS-E fuel distributor which provides for the optimal fuel quantity. Furthermore, the CIS-E control unit provides output signals for operation of the:

^ The fuel pump
^ Idle control valve
^ Transmission shift point delay
^ On-Off ratio output (Diagnostic Socket)
^ "Check Engine" warning lamp

ON-BOARD DIAGNOSTICS

While the engine is running, malfunctions that are encountered and recognized, such as, short circuits and implausible values are stored in the CIS-E control unit. Faults due to intermittent contacts are also recognized and stored as malfunctions. The stored faults can be extracted by use of an impulse counter at the on-board diagnostic connector, or the Mercedes Benz On/Off ratio tester. The battery or the CIS-E control unit must not be disconnected before code extraction is completed or faults will be erased. On Federal models the "CHECK ENGINE" light in the instrument panel will illuminate if a fault is recognized in the oxygen sensor system.