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With Manufacturer's Scan Tool



Engine Coolant Temperature Sensor, Checking

NOTE: Engine Control Module (ECM) will use the intake air temperature as a replacement value for an engine start (start temperature replacement value) when a malfunction is stored in DTC memory that affects the Engine Coolant Temperature (ECT) sensor -G62-. The temperature 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
- V.A.G1551 Scan Tool (ST) or VAG1552 mobile scan tool with VAG1551/3 adapter cable
- VAG1598/22 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 V.A.G1551 (VAG1552) Scan Tool (ST). [1][2]Reading and Clearing Diagnostic Trouble Codes
- Turn on ignition 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.

Display Group 4:






- Start engine and run at idle.

Temperature value must increase uniformly.

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.
- Turn off ignition.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-. Locations

NOTE:
- Display on scan tool jumps by 1.5°C.
- If irregular engine running occurs in certain temperature ranges and the temperature figure does not increase without interruption, the temperature signal is temporarily interrupted and the sensor must be replaced.

- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, generate the readiness code again. Monitors, Trips, Drive Cycles and Readiness Codes

Evaluating display group 004, display field 3 - Coolant temperature

Display Group 4, Display Field 3:






Continuation of check when display approx. -46°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 using auxiliary cables from VW1594 and observe display.
through m.y. 1999: terminals 1 + 3
from m.y. 2000: terminals 4 + 3

If display jumps to approx. 141°C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Turn off ignition.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-. Refer item -19- Locations
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
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. Monitors, Trips, Drive Cycles and Readiness Codes

If display remains at approx. -46°C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Turn off ignition.
- Check wiring according to wiring diagram.

Continuation of check when display at approx. 141 °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. -46 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Turn off ignition.
- Replace Engine Coolant Temperature (ECT) sensor -G62- with Engine Coolant Temperature (ECT) sensor -G2-. Refer item -19- Locations

- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, generate the readiness code again. Monitors, Trips, Drive Cycles and Readiness Codes

If display remains at approx. 141°C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Turn off ignition.
- Check wiring according to wiring diagram.

Checking wiring
- Remove wiper arms and plenum chamber cover.






- Connect VAG1598/22 test box to control module wiring harness.






- 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.
- through m.y. 1999: Terminal -1- + socket 67
- from m.y. 2000: Terminal -4- + socket 67
- Terminal -3- + socket 53
- 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 67
- Terminal -3- + vehicle Ground (GND)
- Specified value: Infinity ohms

- Additionally check both wires for short to battery positive.
Specified value: Infinity ohms

If no malfunction is found in wiring:






- Perform resistance measurement on Engine Coolant Temperature (ECT) sensor -G62-.
through m.y. 1999: terminals 1 + 3
from m.y. 2000: terminals 4 + 3






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-. Refer item -19- Locations
- Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
Reading Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes

- Display readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, generate the readiness code again. Monitors, Trips, Drive Cycles and Readiness Codes

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