Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection

Intake Air Temperature sensor, checking

Special tools, testers, measuring instruments and auxiliary items required

- VAG 1551/1552 Scan Tool with VAG 1551/3B adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 Multimeter
- VW 1594 Adaptor kit
- Wiring diagram
- Chilling spray (commercially available)

NOTE: If sensor or connecting wiring is faulty the Control Module operates with a fixed substitute temperature of 19.5 °C.

Test sequence

- Connect VAG 1551/1552 Scan Tool, [1][2][3]Reading and Clearing Diagnostic Trouble Codes
- Switch ON ignition
- Press 0 and 1 buttons to select "Address word" 01 "Engine electronics"
Display will appear as shown

Rapid data transfer HELP
Select function XX

- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input

Display will appear as shown

Read measuring value block HELP
Input Display group number XXX

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

Display will appear as shown (1 to 4 = Display zones)

Read measuring value block 4 ->
1 2 3 4

- Check specification for Intake Air Temperature sensor, Display zone 4:






Evaluating Display group 4







Continuation check when Display reads approx. - 46 °C

- Disconnect harness connector -1- from Intake Air Temperature sensor G42 -2-.








- Bridge connector terminals using jumper wires from W 1594 adaptor kit and observe display.

When display reaches approx. 141 °C

- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Replace intake Air Temperature sensor G42.

When Display is approx. - 46 °C:

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

Continuation check when display reads approx. 141 °C

- Disconnect harness connector -1- from Intake Air Temperature sensor G42 -2-.







When Display is approx. - 46 °C:

- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input
- Switch OFF ignition.
- Replace Intake Air Temperature sensor G42.

When Display is approx. 141 °C

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

Continuation of check when Display ambient temperature:

- Disconnect Intake Air Temperature sensor harness connector







- Re-connect harness connector
- Note Intake Air Temperature value in shown in Display zone 4.
- Spray sensor with commercial chilling agent while observing temperature value
- displayed temperature value must decrease
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End data output"
- Press Q button to enter input

Wiring, checking

- Connect VAG 1598/22 Test Box to Engine Control Module harness connector.






- Disconnect harness connector -1- from Intake Air Temperature sensor G42 -2-.







- Check wire for open circuit between Test Box socket 67 + 2-pin harness connector terminal 2 using Wiring diagram.

- Wire resistance: Max. 1.5 Ohms

- Check wire for open circuit between Test Box socket 54 + 2-pin harness connector terminal 1 using Wiring diagram.

- Wire resistance: Max. 1.5 Ohms

- Check wiring for short circuit to Battery +.
- Specification: Infinity Ohms

If wiring OK

- Measure resistance between intake Air Temperature sensor G42 terminals 1 (signal) and 2 (Ground)







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







Examples:
- 30 °C is in range A and corresponds to 1.5 to 2.0 k Ohms
- 80 °C is in range B and corresponds to 275 to 375 Ohms

If specification not obtained
- Replace Intake Air Temperature sensor G42.

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

NOTE: If DTC memory has been erased or the Engine Control Module was disconnected from its Voltage supply, the Readiness Code must be created again , Monitors, Trips, Drive Cycles and Readiness Codes