Engine coolant temperature (ECT) sensor -G62-, testing

Special tools and equipment 

• VAG 1526 A
• VAG 1594 A
• VAG 1598/31
• VAS 5051 with VAS 5051/1

Fitting location. Refer to Component locations, overview. Refer to Component locations overview 

Test requirement: 

• Engine cold

Test sequence 

• Connect the vehicle diagnostic, testing and information system VAS 5051. Refer to Vehicle diagnostic, testing and information system VAS 5051, connecting and selecting functions , and select the vehicle system "01 - Engine electronics" from the menu. When doing this the engine should be idling.

Display on VAS 5051:

• Select the diagnosis function "08 - Read data block" from the menu -1-.

Display on VAS 5051:

1 - Enter display group

(figures up to 255)

• Using the keypad -2-, enter "004" to select Display group 004 and confirm entry with Q button.

Display on VAS 5051:

• Check display value for engine coolant temperature sensor (display zone -3-).

	Display zones
	1	2	3	4
Display Group 004: Coolant temperature with engine idling
Display	xxxx RPM	xx.x V	xxx.x °C	xxx.x °C
Indicates	Engine speed	Battery voltage	Coolant temperature	Intake air temperature
Range			-48.0 to 143.0 °C
Specification	xxxx RPM	12.0 to 15.0 V	Temperature display should rise steadily	Between ambient temperature and 110 °C

• Press the ← button to exit from the function "08 - Read data block".

If display zone 3 shows an implausible value:

• Unplug connector on engine coolant temperature sensor.

• Connect multimeter (resistance test range) between contacts C and D on the sender.

Scale A shows resistance values for temperature range 0 to 50 °C and scale B the values for temperature range 50 to 100 °C.

Examples:

• 30 °C corresponds to a resistance from 1500 to 2000 Ω
• 80 °C corresponds to a resistance from 275 to 375 Ω

If the specification is not attained:

• Fit a new engine coolant temperature sensor.

If the specification is obtained:

• Connect test box VAG 1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself. Refer to Wiring and component check using test box VAG 1598/31 .

• Test for open circuit and short to positive or Ground in the following wiring connections:

Connector  Contact	Test box VAG 1598/31  Socket
3 (signal)	93
4	108

• Test for short circuits between the two wires.
• Correct any open/short circuit as necessary.

If no fault is detected:

• Fit a new engine control module. Refer to Engine Control Module (ECM) (without metal anti-theft housing), replacing .