Test sequence

WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

Connect vehicle diagnostic, testing and information system VAS 5051. See VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM, CONNECTING AND SELECTING FUNCTIONS . Select vehicle system "01 - Engine electronics" in selection. Engine must be run at idle.
Display on VAS 5051:

Fig 1: Identifying Display On VAS 5051 - Engine Coolant Temperature Sensor (1 Of 3)
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Under -1- select diagnostic function "08 - Read measured value block".
Display on VAS 5051:

Fig 2: Identifying Display On VAS 5051 - Engine Coolant Temperature Sensor (2 Of 3)
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1. Enter display group
Enter "004" for "display group number 004" in zone -2- and confirm entry by pressing -Q- button.

Display on VAS 5051:

Fig 3: Identifying Display On VAS 5051 - Engine Coolant Temperature Sensor (3 Of 3)

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Check Engine Coolant Temperature (ECT) sensor -G62- in display zone -3-.

DISPLAY GROUP 004: COOLANT TEMPERATURE WITH ENGINE AT IDLE

	Display zones
	1	2	3	4
Display group 004: Coolant temperature with engine at idle
Display	xxxx rpm	xx.x V	xxx.x °C	xxx.x °C
Display	Engine speed	Battery voltage	Coolant temperature	Intake Air Temperature (IAT)
Range			-48.0...143.0 °C
Specified value	xxxx rpm	12.0...15.0 volts	The temperature reading should increase evenly	from ambient temperature up to 110 °C

If display zone 3 shows an implausible value:

Disconnect Engine Coolant Temperature (ECT) sensor connector at -G2- / -G62- -arrow-.

Fig 4: Disconnecting Engine Coolant Temperature Sensor Connector

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Connect multimeter between terminals C and D of sensor to measure resistance.

Fig 5: Identifying ECT Sensor Connector Terminals
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Range A shows resistance values for temperature range 0...50 °C and range B shows the values for temperature range 50...100 °C.

Sample readings:
- 30 °C corresponds to a resistance of 1500...2000Ω
- 80 °C corresponds to a resistance of 275..375Ω
Fig 6: Identifying ECT Sensor Temperature Versus Resistance
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If specified value is not obtained:

Replace Engine Coolant Temperature (ECT) sensor -G62-.

If specified value is obtained:

Connect test box V.A.G 1598/31 to wiring harness for ECM; do not connect directly to the ECM. See ELECTRICAL TESTING USING VAG1598/31 TEST BOX .
Check for open circuit, short to positive, or short to ground in following wiring connections:

Fig 7: Identifying ECT Sensor Harness Connector Terminals

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ECT SENSOR CIRCUIT CHECK: TERMINAL 3, 4 & SOCKET 108, 93

Connector terminal	Test box V.A.G 1598/31 Socket
3	108
4 (signal)	93

Test for short circuits between two wires.
Repair any open/short circuit as necessary.

If no wiring problems are found:

Replace ECM. See ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING .