300E 4MATIC (124.230) L6-3.0L (103.985) (1990)
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EGR Control Solenoid: Description and Operation
Switchover Valve Locations
The CIS-E control unit controls exhaust gas recirculation via the EGR switchover valve. The switchover valve connects the EGR valve to vacuum from
the throttle valve assembly.
During deceleration the EGR switchover valve is operated for 1.5 seconds. From the intake manifold pressure signal, which is measured by the ignition
control unit, it can be determined whether the EGR system is working. If a fault is recognized, it is stored in the malfunction memory of the CIS-E
control unit. If the period of deceleration is less than 1.5 seconds, the test is canceled.
Exhaust gas recirculation operates if:
^
Coolant temperature is greater the 140°F
^
Potentiometer voltage at the air flow sensor position indicator is greater than 2V.
^
Full load contact of the throttle valve switch is open.
^
Idle speed contact of the throttle valve switch is open.
