With Manufacturer's Scan Tool
Intake Air Temperature (IAT) Sensor -G42-, Checking
Special tools and equipment
- VAG 1551 Scan Tool or VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/22
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram
- Chilling spray (commercially available)
NOTE: If sensor or connecting wiring is faulty the control module operates with a substitute temperature of 19.5 degree C.
Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Then switch ignition on and select engine control module with "Address word" 01. (Connecting scan tool and selecting engine control module).
Indicated on display data
Rapid transfer HELP
Select function XX
- Press keys 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q key.
Indicated on display
Read Measuring Value Block HELP
Input display group number XX
- 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 Measuring Value Block 4 ->
1 2 3 4
Functional check of sensor
- Read intake air temperature value in display zone 4.
Specification: approx. ambient temperature
If the specification is not obtained:
- Perform check according to following table:
Display1) Cause
Approx. -46 degree C Open circuit or short to positive
Approx. 141 degree C Short to Ground
1) If a temperature is displayed which deviates greatly from the ambient temperature of the sensor, check sensor wiring for transfer resistances.
If the specification is obtained:
- Remove intake air temperature sensor. Attach connector again.
- Note intake air temperature value in display zone 4.
- Spray sensor with commercial chilling agent while observing the 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. -46 degree C:
- Pull connector -1- off intake air temperature sensor -2-.
- Bridge connector contacts using auxiliary cables from VAG 1594 and observe display.
If display remains at approx. 141 degree 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 sensor.
If display jumps to approx. -46 degree 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.
Continuation of check when display reads approx. 141 degree C:
- Pull connector -1- off intake air temperature sensor -2-.
If display jumps to approx. -46 degree 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 sensor.
If display remains at approx. 141 degree 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 test box VAG 1598/22 to control module wiring harness.
- Pull connector -1- off intake air temperature sensor -2-.
- Check wiring between test box and 2 pin connector for open circuit according to wiring diagram.
Contact 1 + socket 54
Contact 2 + socket 67
Wire resistance: Max. 1.5 Ohm
- Additionally check both wires for short to battery positive.
If no wiring malfunction is detected:
- Perform resistance measurement at intake air temperature sensor contacts 1 (signal) and 2 (Ground)
Scale A shows resistance values for temperature range 0 to 50 degree C and scale B the values for temperature range 50 to 100 degree C.
Examples:
- 30 degree C is in range A and corresponds to a resistance of 1.5 to 2.0 kOhms
- 80 degree 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-.
If there is no malfunction in the wiring and the resistance measurement values are OK.:
- Replace engine control module.