Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI1998A8 SEDAN (4D2) V8-3.7L (AEW)REPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSCOOLANT TEMPERATURE SENSOR/SWITCH (FOR COMPUTER)TESTING AND INSPECTIONENGINE COOLANT TEMPERATURE (ECT) SENSOR -G2- SIGNAL, CHECKING
1998 Audi A8 Sedan (4D2) V8-3.7L (AEW)
Engine Coolant Temperature (ECT) Sensor -G2- Signal, Checking
1998 Audi A8 Sedan (4D2) V8-3.7L (AEW)SECTION 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.
- 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", Testing and Inspection
- 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 Testing and Inspection
- 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.
- Remove instrument cluster.
- Connect VAG1598 to blue 32-pin connector using the VAG1598/25 adapter.
- Measure resistance between socket 3 and socket 5 (sensor Ground -GND-) using multimeter (Fluke 83 or equivalent)
Specified values:
- Coolant temperature 90 °C: approx. 110 Ohm
- Coolant temperature 120 °C: approx. 50 Ohm
Check wire connection to Engine Coolant Temperature (ECT) sensor -G2- if specified values are not obtained.
- Check wire connection according to wiring diagram.
- If specified values are not obtained, Engine Coolant Temperature (ECT) sensor -G2- must be replaced.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.