With Manufacturer's Scan Tool

Intake Air Temperature (IAT) Sensor, Checking


NOTE: Only gold-plated terminals must be used to repair the terminals in the Intake Air Temperature (IAT) sensor.


Special tools, test equipment and auxiliary items
- VAG 1551 scan tool or VAG 1552 mobile scan tool with VAG 1551/3B cable
- VAG 1598/31 test box
- VAG 1526 hand multimeter or VAG 1715 multimeter
- VAG 1594 adapter set
- Electrical Wiring Diagram
- VAG 1921 pliers for spring type clips
- Chilling spray (commercially available)

Test sequence
- Connect VAG 1551 scan tool ((VAG 1552). Switch ignition on and select Motronic Engine Control Module (ECM) -J220- with "Address word" 01. Connecting scan tool and selecting Motronic Engine Control Module (ECM) -J220-. [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 to 4 = Display zones)


Read measuring value block 4 ->
1 2 3 4


- Read off intake air temperature value in display zone 4.

Specification: approx. ambient temperature







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

Evaluating display group 4, display zone 4 - Intake air temperature







If the specification is obtained:

Continuation of check when display = ambient temperature:







- Disconnect 2-pin connector -arrow- from Intake Air Temperature (IAT) sensor -G42-.







- Remove Intake Air Temperature (IAT) sensor -arrow-.
- Re-connect 2-pin connector.
- Note intake air temperature value in display zone 4.







- Spray sensor -arrow- with commercial chilling agent while observing temperature value.
Temperature value must decrease.

If the specification is not obtained:
- Press -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with -Q- button.
- Switch off ignition.

Continuation of check when display reads approx. -48.0 °C:







- Disconnect connector -1- from Intake Air Temperature (IAT) sensor -G42- -2-.
- Bridge connector terminals using aux. cables from VAG 1594 and observe display.

If display jumps to approx. 143.0 °C:
- Press -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with -Q- button.
- Switch off ignition.
- Replace Intake Air Temperature (IAT) sensor -G42-, item 26.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory, Checking and Erasing DTC Memory. Reading Diagnostic Trouble Codes
- Read readiness code. If DTC memory has been erased or Motronic Engine Control Module (ECM) -J220- was disconnected from battery 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. -48.0 °C:
- Press -> button.
- Press buttons 0 and 6 for function "End output" and confirm entry with Q button.
- Switch off ignition.
- Check wiring using Electrical Wiring Diagram.

Continuation of check when display reads approx. 143 °C:







- Disconnect connector -1- from Intake Air Temperature (IAT) sensor -2-.

If display jumps to approx. -48.0 °C:
- Press -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with -Q- button.
- Switch off ignition.
- Replace Intake Air Temperature (IAT) sensor -G42-, item 26.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory, Checking and Erasing DTC Memory. Reading Diagnostic Trouble Codes
- Read readiness code. If DTC memory has been erased or Motronic Engine Control Module (ECM) -J220- was disconnected from battery 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. 143 °C:
- Press -> button.
- Press buttons -0- and -6- for function "End output" and confirm entry with -Q- button.
- Switch off ignition.
- Check wiring using Electrical Wiring Diagram.

Checking wiring
- Remove inner plenum chamber cover, left.







- Connect VAG 1598/31 test box to control module wiring harness. Motronic Engine Control Module (ECM) -J220- is not connected by this action.







- Disconnect connector -1- from Intake Air Temperature (IAT) sensor -2-.







- Check wiring between test box and 2-pin connector -1- for open circuit according to Electrical Wiring Diagram.
- Terminal 1 + Socket 85
- Terminal 2 + Socket 108

Wire resistance: max. 1.5 Ohms

- Additionally check both wires for short to battery positive.

Specification: Infinity Ohms

If no wiring malfunctions are detected:







- Perform resistance measurement on Intake Air Temperature (IAT) sensor -G42- terminals 1 (signal) and 2 (ground).







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

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

If the specification is not obtained:
- Replace Intake Air Temperature (IAT) sensor -G42-, item 26.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory, Checking and Erasing DTC Memory. Reading Diagnostic Trouble Codes
- Read readiness code. If DTC memory has been erased or Motronic Engine Control Module (ECM) -J220- was disconnected from battery 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 Motronic Engine Control Module (ECM) -J220-.