A8 Quattro Sedan V8-4.2L (AUX) (2001)
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Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
Engine Coolant Temperature (ECT) Sensor -G2- Signal, Checking
Engine Coolant Temperature (ECT) Sensor -G2- Signal, Checking
If the coolant temperature display in the instrument cluster shows an incorrect reading, first check whether the signal is received by the instrument
cluster.
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Connect VAS5051 tester or VAG1551 Scan Tool (ST). Refer "Scan Tool Testing/Scan Tool Connecting And Initial Checks/Connecting and
Selecting Functions VAS5051 Tester/VAG1551 Scan Tool". Under "Lighting and Horns/Headlamp", See: Lighting and Horns/Headlamp/Testing
and Inspection
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Read Measuring Value Block. Refer to "Instrument Cluster, On Board Diagnostic (OBD)/Scan Tool Testing/ Measuring Value Blocks/", Under
Instrument Panel, Gauges and Waring Indicators/Instrument Panel See: Instrument Panel, Gauges and Warning Indicators/Instrument Cluster /
Carrier/Testing and Inspection
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Press buttons -0-, -0- and -3- to input display group number 003, and press -0- button to confirm input.
If the VAG1551 scan tool displays the coolant temperature, but the coolant temperature display in the instrument cluster does not, then the instrument
cluster is malfunctioning and must be replaced.
If the VAG1551 scan tool also does not display a coolant temperature, then the signal must be checked at the multi-pin connector of the instrument
cluster.
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Remove instrument cluster.
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Connect VAG1598 to blue 32-pin connector using the VAG1598/25 adapter.
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Measure resistance between socket 3 and socket 5 (sensor Ground -GND-) using multimeter (Fluke 83 or equivalent)
Specified values:
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Coolant temperature 90 °C: approx. 110 Ohm
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Coolant temperature 120 °C: approx. 50 Ohm
Check wire connection to Engine Coolant Temperature (ECT) sensor -G2- if specified values are not obtained.
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Check wire connection according to wiring diagram.
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If specified values are not obtained, Engine Coolant Temperature (ECT) sensor -G2- must be replaced.
