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With Manufacturer's Scan Tool



Intake Air Temperature (IAT) Sensor -G42-, Checking

Special tools and equipment
- V.A.G1551 scan tool or V.A.G1552 mobile scan tool with V.A.G1551/3B cable
- V.A.G1598/31 test box
- V.A.G1526 or Fluke 83 multimeter
- V.A.G1594 adapter set
- Wiring diagram
- Chilling spray (commercially available)

Test sequence
- Connect V.A.G1551 scan tool (V.A.G1552). Switch ignition on and select engine control module with "Address word" 01. (Connecting scan tool and selecting engine control module. [1][2][3]Connecting VAG 1551 Scan Tool)

Indicated on display:

Rapid data transfer HELP
Select function XX

- Press keys 0 and 8 for function "Read measured value block" and confirm entry with Q key.

Indicated on display:

Read measured value block HELP
Input display group number XXX

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

Indicated on display: (1 to 4 = Display zones)

Read measured 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:

Display1) Cause
approx. -48 degrees C Open circuit or short to positive
approx. 143 degrees C Short to Ground (GND)

1)If a temperature is displayed which is below the ambient air temperature of the sensor, check sensor wiring for transfer resistances. Note when doing this that sensor is heated from external sources, e.g. radiated heat when engine is not running.

If the specification is obtained:







- Remove Intake Air Temperature (IAT) sensor. Attach connector again.
- Note intake air temperature value in display zone 4.
- Spray sensor with commercial chilling agent while observing temperature value. Temperature value must decrease.
- Press -> key.
- Press keys 0 and 6 for function "End output" and confirm entry with Q key.

Continuation of check when display reads approx. -48 degrees C







- Disconnect connector -1- from Intake Air Temperature (IAT) sensor -G42- -2-.
- Bridge connector contacts using auxiliary cables from V.A.G1594 and observe display.

If display jumps to approx. 143 degrees C:
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with Q key.
- Switch ignition off.
- Replace intake air temperature (IAT) sensor -G42-.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory. DTC Memory, Checking and Erasing (Functions 02 and 05)
- 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. -48 degrees C:
- Press -> key.
- Press keys 0 and 6 for the function "End output" and confirm entry with Q key.
- Switch ignition off.
- Check wiring using wiring diagram.

Continuation of check when display reads approx. 143 degrees C







- Disconnect connector -1- from intake air temperature (IAT) sensor -G42- -2-.

If display jumps to approx. -48 degrees C:
- Press -> key.
- Press keys 0 and 6 for function "End output" and confirm entry with Q key.
- Switch ignition off.
- Replace intake air temperature (IAT) sensor -G42-.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory. DTC Memory, Checking and Erasing (Functions 02 and 05)
- Read-out 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

If display remains at approx.143 degrees C:
- Press -> key.
- Press keys 0 and 6 for function "End output" and confirm entry with Q key.
- Switch ignition off.
- Check wiring using wiring diagram.

Checking wiring







- Connect V.A.G1598/31 test box to control module wiring harness. Engine control module remains disconnected.







- Disconnect connector -1- from intake air temperature (IAT) sensor -G42- -2-.
- Check wiring between test box and 2-pin connector -1- for open circuit using wiring diagram.
Contact 1 + socket 85
Contact 2 + socket 108
Wire resistance: max. 1.5 Ohms

- Check both wires for short to battery positive.

If no malfunction in wire is detected:







- Perform resistance measurement on intake air temperature (IAT) sensor -2- -G42-.







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

Examples:
- 30 degrees C is in range A and corresponds to a resistance of 1.5 to 2.0 k Ohms
- 80 degrees 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-.
- Check DTC Memory, if necessary, repair any malfunctions and then Erase DTC Memory. With Manufacturer's Scan Tool
- 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

If there is no malfunction in the wiring and the resistance measurement values are OK.
- Replace engine control module.
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