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With Manufacturer's Scan Tool




Engine Coolant Temperature (ECT) Sensor, Checking


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


Special tools and equipment
- Scan tool VAG 1551 or vehicle system tester V.A.G 1552 with cable VAG 1551/3B
- Test box V.A.G 1598/31
- Hand multimeter V.A.G 1526 or multimeter VAG 1715
- Adapter set V.A.G 1594
- Wiring diagram

Test conditions
- Engine must be cold

Test sequence


NOTE: Only gold-plated terminals must be used to repair the terminals in the connector for the Engine Coolant Temperature (ECT) sensor.


- Connect scan tool VAG 1551 (V.A.G 1552). Then switch ignition on and select engine control module with "Address word" 01.
Connecting scan tool and selecting Engine Control Module (ECM). [1][2][3]Connecting VAG 1551 Scan Tool

Indicated on display


Rapid data transfer HELP
Select function XX


- Press buttons 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q button.

Indicated on display


Read Measuring Value Block
Input display group number XXX


- Press buttons 0, 0 and 4 for "Display group number 4" and confirm entry with Q button.

Indicated on display (1-4 = Display zones)


Read Measuring Value Block 4 ->
1 2 3 4


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

If the specification is not obtained:
- Perform check according to following table:







If the specification is obtained:
- Start engine and run at idling speed. Temperature value must increase uniformly


NOTE:
- The temperature rises in steps of 1.0 °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.
- Only gold-plated terminals must be used to repair the terminals in the connector for the coolant temperature sensor.


- Press -> button.
- Press buttons 0 and 6 for the "End output" function and confirm input with Q button.

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







- Disconnect 4 pin connector off Engine Coolant Temperature (ECT) sensor (G62) with coolant temperature gauge sensor (G2) - arrow-.







- Bridge connector terminals 3 + 4 using auxiliary cables from V.A.G 1594 and observe display.

If display jumps to approx. 140 °C:
- Press -> button.
- Press buttons 0 and 6 for "End output" function and confirm input with Q button.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor (G62)
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory. Reading Diagnostic Trouble Codes
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes

If display remains at approx. -40 °C:
- Press -> button.
- Press buttons 0 and 6 for "End output" function and confirm input with Q button.
- Switch ignition off.
- Check wiring using wiring diagram.

Continuation of check when display approx. 140 °C:







- Disconnect the 4 pin connector off Engine Coolant Temperature (ECT) sensor (G62) with coolant temperature gauge sensor (G2) - arrow-.

If display jumps to approx. -40 °C:
- Press -> button.
- Press buttons 0 and 6 for "End output" function and confirm input with Q button.
- Switch ignition off.
- Replace Engine Coolant Temperature (ECT) sensor (G62)/coolant temperature gauge sensor (G2)
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory. Reading Diagnostic Trouble Codes
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes

If display remains at approx. 140 °C:
- Press -> button.
- Press buttons 0 and 6 for "End output" function and confirm input with Q button.
- Switch ignition off.
- Check wiring using wiring diagram.

Checking wiring
- Remove inner plenum chamber cover, left:







- Connect test box V.A.G 1598/31 to control module wiring harness. Engine control module is not connected by this action.







- Disconnect 4 pin connector off Engine Coolant Temperature (ECT) sensor (G62) with coolant temperature gauge sensor (G2) - arrow-.







- Check wire for open circuit between test box and 4-pin connector using wiring diagram.
- Terminal 3 + Socket 93
- Terminal 4 + Socket 108
Wire resistance: max. 1.5 Ohms

- Check wire for short circuit between test box and 4-pin connector terminal 4 to wire terminal 3 and to vehicle Ground using wiring diagram.
- Terminal 3 + socket 108
- Terminal 3 + vehicle Ground

Specification: Infinity Ohms
- Additionally check both wires for short to battery positive.
Specification: Infinity Ohms

If no wiring malfunctions are detected:







- Perform resistance measurement on Engine Coolant Temperature (ECT) sensor (G62) terminal C (signal) and D (Ground).







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


Examples:
- 30 °C corresponds to a resistance from 1.5 to 2.0 k Ohms
- 80 °C corresponds to a resistance from 275 to 375 Ohms

If the specification is not obtained:
- Replace Engine Coolant Temperature (ECT) sensor (G62).
- Check DTC memory, if necessary, repair any malfunctions and then erase DTC memory. Reading Diagnostic Trouble Codes
- Read readiness code. If DTC memory has been erased or engine control module was disconnected from permanent positive, readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
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.
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