With Manufacturer's Scan Tool

Engine Coolant Temperature Sensor, checking

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required
- VAG 1551/1552 Scan Tool using VAG 1551/3 Adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 multimeter
- VW 1594 Adaptor kit
- Wiring diagram

Requirement
- Engine must be cold


NOTE:
The Engine Control Module (ECM) uses Intake Air Temperature as a replacement value for engine starting (start temperature replacement value) if 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 ECM. Shortly after the engine reaches operating temperature a constant replacement value will be displayed. This value is also dependent upon Intake Air Temperature.

Test sequence
- Connect VAG 1551/1552 Scan Tool.
- Switch ON ignition.
- Press 0 and 1 buttons to select "Engine Electronics" address word 01.

Indicated on display (example only)


06A906018AB Motronic M5.9.2 HS V06 ->
Coding 00000 WSC 00000


- Press -> button.

Indicated on display


Rapid data transfer HELP
Select function XX


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

Indicated on display


Read measuring value block
Input Display group number XXX


- Press buttons 0, 0 and 4 for "Display group 4."
- Press Q button to enter input.

Indicated on display (1 to 4 = Display fields)


Read measuring value block 4 ->
1 2 3


- Note Engine Coolant Temperature value in Display field 3.







- Start engine and let idle.
- Temperature value must increase uniformly

If specification not obtained
- Press -> button.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press 0 and 6 buttons to select "End output" function 06.
- Press Q button to enter input.
- Switch OFF ignition.
- Replace Engine Coolant Temperature sensor G62.


NOTE:
- Scan Tool display jumps by 1.5 °C increments.
- If the engine runs irregularly in certain temperature ranges and the temperature value does not smoothly increase without interruption, the signal is intermittent and the ECT sensor must be replaced.

Evaluating Display group 4







Check continuation when display = approx. - 46 °C







- Disconnect 4-pin harness connector -1- from ECT sensor -2-.
- Bridge connector terminals 1 + 3 using jumper wires from VW 1594 Adaptor kit and observe display.

When display is approx. 141 °C, press -> button.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press 0 and 6 buttons to select "End output" function 06.
- Press Q button to enter input.
- Switch OFF ignition.
- Replace Engine Coolant Temperature sensor G62.

When display value is approx. - 46 °C
- Press -> button.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press 0 and 6 buttons to select "End output" function 06.
- Press Q button to enter input.
- Switch OFF ignition.
- Check wiring using Wiring diagram.

Check continuation when display = approx. 141 °C







- Disconnect 4-pin harness connector -1- from ECT sensor -2-.

When display is approx. -46 °C:
- Press -> button.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press 0 and 6 buttons to select "End output" function 06.
- Press Q button to enter input.
- Switch OFF ignition.
- Replace Engine Coolant Temperature sensor G62.

When display is approx. 141 °C
- Press -> button.

Indicated on display


Rapid data transfer HELP
Select function XX


- Press 0 and 6 buttons to select "End output" function 06.
- Press Q button to enter input.
- Switch OFF ignition.
- Check wiring using Wiring diagram

Wiring, checking







- Connect VAG 1598/22 Test Box to ECM wiring harness.







- Disconnect 4-pin harness connector -1- from ECT sensor -2-.
- Check wire for open circuit between Test Box socket 67 and 4-pin harness connector terminal 1 using Wiring diagram.
- Wire resistance: 1.5 Ohms maximum
- Check wire for open circuit between Test Box socket 53 and 4-pin harness connector terminal 3 using Wiring diagram.
- Wire resistance: 1.5 Ohms maximum
- Check for short between Test Box and 4-pin harness connector terminals 1 and 3 to vehicle Ground, using Wiring diagram.
- Terminal 3 + socket 67
- Terminal 3 + vehicle Ground

Specification: Infinity Ohms
- Also check both wires for short to Battery +.
Specification: Infinity Ohms

If wiring OK:







- Measure resistance between ECT sensor terminals 1 (ground) and 3 (signal).







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

Examples:
- 30 °C (range A) corresponds to a resistance of 1.5 to 2.0 k Ohms
- 80 °C (range B) corresponds to a resistance of 275 to 375 Ohms

If specification not obtained
- Replace ECT sensor G62.
- Display the Readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
- If DTC memory was erased or if the ECM was disconnected from Battery + , set the Readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If wiring OK and resistance measurement values OK
- Replace Engine Control Module.