Test sequence

If a malfunction of the Engine Coolant Temperature (ECT) gauge is detected at the instrument cluster, check if the signal at the instrument cluster is OK.

Read measuring value block display group 003.
See MEASURING VALUE BLOCK 003 .
Check indication in display field -1-.

Fig 1: Scan Tool Display - Signal From Coolant Temperature Sensor

Courtesy of AUDI OF AMERICA, INC.

If the coolant temperature is indicated, instrument cluster is malfunctioning.

Replace instrument cluster. See INSTRUMENT CLUSTER, REMOVING AND INSTALLING .

If the Engine Coolant Temperature (ECT) is not indicated:

Check signal at multi-pin harness connector at instrument cluster.
Remove instrument cluster. See INSTRUMENT CLUSTER, REMOVING AND INSTALLING .
Connect VAG 1598A test box to blue 32-pin multi-pin harness connector using VAG 1598/25 adapter.
Connect multimeter between terminal 8 and 7 (sensor Ground (GND)) for resistance measurement.

ENGINE COOLANT TEMPERATURE RESISTANCE SPECIFICATION

Engine coolant temperature in °C	Resistance in ohm
90	approx. 110
120	approx. 50

If specified values are not obtained:

Check wire connection between instrument cluster and Engine Coolant Temperature (ECT) sensor according to wiring diagram.

If no malfunctions are found in wire:

Replace coolant temperature sensor.