Engine Coolant Temperature (ECT) Sensor, Checking

Special tools and equipment
- V.A.G 1551 scan tool (or VAG 1552 mobile scan tool) with VAG 1551/3B cable
- VAG 1598/31 adapter cable
- VAG 1526 multimeter or VAG 1715 multimeter
- VAG 1594 connector test kit
- Wiring diagram

Test requirement
- Engine must be cold.

Test sequence
- Connect V.A.G 1551 scan tool (VAG 1552). Then switch ignition on and select the Engine Control Module (ECM) using address word 01. (connecting scan tool and selecting ECM). [1][2][3]Connecting VAG 1551 Scan Tool

Indicated on display:


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read measuring value block" function 08. Press -Q- button to confirm input.

Indicated on display:


Read measuring value block HELP
Enter display group number XX


- Press buttons -0-, -0- and -4- to select "Display group number 4". Press -Q- button to confirm input.

Indicated on display: (1 to 4 - display fields)


Read measuring value block 4 ->
1 2 3 4


- Read coolant temperature value in display field 3. Specification: approx. coolant temperature

If specified value is not obtained:
- Continue test according to the following table:







If specified value is obtained:
- Start engine and let run at idle. Temperature value must rise evenly


NOTE:
- The temperature climbs in increments of 1.0 °C.
- If the engine shows problems in certain temperature ranges and if the temperature does not climb uniformly, the temperature signal is intermiffent and the sensor should be replaced.


- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06. Press -Q- button to confirm input.

Continuation of test if indication is approx. -48 °C:

I - Engine code ATW
II - Engine codes AUG, AWM







- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) sensor -G62- (item no. 2).







- Bridge terminals 3 + 4 of connector using adapter cables from VAG 1594 connector test kit, and observe what is indicated on display.

If indication jumps to approx. 143 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor (G62).

If indication remains approx. -48 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Check wires according to wiring diagram

Continuation of test if indication is approx. 143 °C:

I - Engine code ATW
II - Engine codes AUG, AWM







- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) sensor -G62- (item no. 2).

If indication jumps to approx. -48 °C:
- Press -> button.
- Press buttons -0 and -6- to select "End data transfer" function 06 Press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor (G62).

If indication remains at approx. 143 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End data transfer" function 06. Press -Q- button to confirm input.
- Switch ignition off.
- Check wires according to wiring diagram

Checking wiring







- Connect VAG 1598/31 adapter cable to control module wiring harness. Engine Control Module (ECM) is not connected.

I - Engine code ATW
II - Engine codes AUG, AWM







- Disconnect 4-pin connector -1- from Engine Coolant Temperature (ECT) sensor -G62- (item no. 2).







- Check wires between test box and 4-pin connector for open circuits according to wiring diagram.
Terminal 4 + socket 93
Terminal 3 + socket 108
Wire resistance: max: 1.5 Ohms
- Also check wires for short circuit to each other.
- Also check wires for short circuits to B+ or Ground (GND).

If no malfunctions are found in wires:







- Measure resistance at Engine Coolant Temperature (ECT) sensor -G62-, terminals B (Ground -GND-) and D (signal).







Range A shows the resistance values for the temperature range from 0-50 °C, and range B shows the values for the temperature range from 50-100 °C.

Read-out examples:
- 30 °C is in range A and corresponds to a resistance of 1.5 to 2.0 kOhms
- 80 °C is in range B and corresponds to a resistance of 275 to 75 Ohms

If specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) sensor (G62).

If no malfunctions are found in the wires and the resistance values are OK:
- Replace Engine Control Module (ECM).