V8 Quattro V8-3562cc 3.6L DOHC (PT) (1990)
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Heated Oxygen Sensor Module: Description and Operation
Oxygen Sensor Heating System
The Heated Oxygen Sensor Control Module is energized via the Motronic control module. ON or OFF status of the relay depends on several
conditions:
Relay ON conditions
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If the intake air temperature is below 62°F (16°C), when starting the engine, the relay will be turned ON when the coolant temperature
reaches 104°F (40°C).
This should allow enough time for any condensation that might be on the oxygen sensor to evaporate.
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If the air temperature is above 62°F (16°C) when starting the engine, the relay is turned ON immediately.
Relay OFF conditions
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The relay is turned OFF at high engine speed and load to prevent overheating of the oxygen sensors ceramic heating element.
