A8 Sedan V8-3.7L (AEW) (1997)
Temperature Gauge: Testing and Inspection
If the engine coolant temperature gauge is inoperative:
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Check for engine coolant temperature signal at instrument cluster as follows.
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Connect VAG 1551 Scan Tool. See: Testing and Inspection
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Select "Read Measuring Value Block" function 08. See: Testing and Inspection
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Select channel 003.
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If the engine coolant temperature signal is indicated on the VAG 1551 Scan Tool display, the instrument cluster is faulty and must be replaced.
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If the engine coolant temperature signal is NOT indicated on the VAG 1551 Scan Tool display, the signal must be checked at the multi-pin
terminal on the rear of the instrument cluster as follows:
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Remove instrument cluster. See: Instrument Cluster/Service and Repair/Procedures
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Connect test box VAG 1598 and adapter cable VAG 1598/4 to yellow 26-pin connector for instrument cluster.
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Using Fluke 83 multimeter, check resistance between terminals 17 and 12 (GND).
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Coolant temperature 90 °C (194 °F): approx. 110 Ohms
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Coolant temperature 120 °C (248 °F): approx. 50 Ohms
If the correct value is NOT achieved:
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Check wiring to engine coolant temperature sensor using applicable wiring diagram.
If wiring is OK:
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Replace engine coolant temperature sensor.