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With Manufacturer's Scan Tool




Engine Coolant Temperature (ECT) Sensor, Checking

NOTE: The Engine Control Module (ECM) will use the intake air temperature as a replacement value for an engine start (start temperature replacement value) as soon as there is a malfunction stored in DTC memory which affects the Engine Coolant Temperature (ECT) sensor -G62-. The temperature then rises according to a model stored in the control module. When the engine has reached normal operating temperature, a fixed replacement value will be displayed after a certain period. This fixed value is also dependent upon the intake air temperature.


Special tools and equipment
- VAG1551 Scan Tool (ST) or VAG1552 mobile scan tool with VAG1551/3 adapter cable
- VAG 1598/31 test box
- Multimeter (Fluke 83 or equivalent)
- VW1594 adapter set
- Wiring diagram

Test conditions
- Engine cold

Test sequence


NOTE: Only gold plated contacts must be used to repair contacts -1- and -3- in the harness connector for the coolant temperature sensor.


- Connect VAG1551 (VAG1552) Scan Tool (ST).
- Switch ignition on and press buttons -0- and -1- to insert "Engine Electronics" address word 01.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.

Indicated on display


Read Measuring Value Block
Input display group number XXX


- Press buttons -0-, -0- and -4- to input display group number 4 (004) and press -Q- button to confirm input.

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


Read Measuring Value Block 4 ->
1 2 3 4


- Read off coolant temperature value in display field 3.
- Start engine and run at idle. Temperature value must increase uniformly.


Display Group 4:






If the specified value is not obtained:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item 23.


NOTE: The temperature rises in steps of 1.0 °C.


- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
- Display readiness code.

If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.

Evaluating display group 4, display field 3 - Coolant temperature


Display Group 4, Display Field 3:






Continuation of check when display approx. -40 °C:







- Disconnect 4-pin harness connector from Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2- (arrow).







- Bridge harness connector terminals -1- + -3- using auxiliary cables from VW1594 and observe display.

If display jumps to approx. 140 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item -23-.
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
- Display readiness code.
- If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.

If display remains at approx. -40 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
- Check wiring according to wiring diagram.

Continuation of check when display approx. 140.0 °C:







- Disconnect 4-pin harness connector from Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2- (arrow).

If display jumps to approx. -40.0 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-, item 23.
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
- Display readiness code.

If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.

If display remains at approx. 140 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.
- Check wiring according to wiring diagram.

Checking wiring
- Remove wiper arms and plenum chamber cover.







- Connect VAG1598/31 test box to Engine Control Module (ECM) wiring harness. Engine Control Module (ECM) is not connected by this action.







- Disconnect 4-pin harness connector from Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2- (arrow).







- Check wiring between test box and 4- pin harness connector for open circuit according to wiring diagram.
- Terminal -1- + socket 108
- Terminal -3 + socket 93
Wire resistance: max. 1.5 ohms

- Check wire between test box and 4- pin harness connector terminal -1- for short to wire terminal -3- or to vehicle Ground (GND) according to wiring diagram.
- Terminal -3- + socket 108
- Terminal -3- + vehicle Ground (GND)
- Specified value: infinity ohms
- Additionally, check both wires for short to battery positive (B+).
Specified value: infinity ohms

If no malfunction is found in wiring:







- Perform resistance measurement on Engine Coolant Temperature (ECT) sensor -G62-, terminal -1- (Ground (GND)) and terminal -3- (signal).







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

Examples:
- 30 °C corresponds to a resistance from 1500-2000 ohms
- 80 °C corresponds to a resistance from 275-375 ohms

If the specified value is not obtained:
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2- item 23. Refer under "Fuel Delivery and Air Induction/Fuel Injector", Service and Repair
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
- Display readiness code.

If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.

If there is no malfunction in the wiring and the resistance measurement values are OK:
- Replace Engine Control Module (ECM).
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