Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

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). Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks/Connecting VAG 1551 Scan Tool", Testing and Inspection

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 C (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).