S4 Sedan L5-2226cc 2.22L DOHC Turbo (AAN) (1992)
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ECM Holding Relay: Description and Operation
Holding Relay
A holding relay is integrated into the Motronic control module. The holding relay is used for starting the engine, power supply for the "Burn-off" of the
hot wire in the mass air flow sensor and output check diagnosis.
When the ignition is switched ON and before the engine is started, the holding relay supplies power to the:
^
Mass air flow sensor
^
Fuel injectors
^
Idle air control valve
^
Wastegate frequency valve
When the ignition is switched OFF, the holding relay supplies power to pin 37 for five (5) seconds. This ensures that the mass air flow sensor has
voltage to burn off (clean) the hot wire.
