V8 Quattro V8-3562cc 3.6L DOHC (PT) (1990)
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EGR Thermo Switch: Description and Operation
Coolant Temperature Sensor V8
DESCRIPTION
The Engine Coolant Temperature (ECT) Sensor is is an electrical thermistor with negative temperature coefficient properties. Negative
temperature coefficient means that as temperature increases, resistance decreases. The ECT signal is used by the Engine Control Module (ECM)
for ignition timing, idle speed control and fuel injection quantity.
In addition, various functions such as oxygen sensor control, deceleration fuel shut-off and evaporative emission system operations are based on
output from the ECT sensor.
SELF DIAGNOSIS
The ECM can recognize an open or shorted sensor or sensor circuit and stores a fault code.
Diagnostic Trouble Code # 00522 is displayed on the VAG 1551 scan tool.
Blink Code # 2312 is displayed using blink code extraction.
SIGNAL SUBSTITUTION
If the ECT signal fails and the intake air temperature is above 40°C (109°F), the ECM substitutes a fixed value equivalant to 80°C (176°F) for the
ECT signal.
