Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection
INTAKE AIR TEMPERATURE SENSOR, CHECKING
Special Tools, Testers And Auxiliary Items
- VAG 1551/1552 scan tool with VAG 1551/3 adapter cable
- VAG 1598/18 test box
- Multimeter (Fluke 83 or equivalent)
- Connector test kit VW 1594
- Wiring diagram
- Chilling spray (commercially available)
Test Sequence
- Connect VAG 1551/1552 scan tool and select "Engine Electronics" address word 01. When doing this the ignition must be switched on.
Indicated on display
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.
Indicated on display
Read Measuring Value Block HELP
Input display group number XXX
- Press buttons -0-, -0- and -3- for display group 003 and press -Q- button to confirm input.
Indicated on display (1-4 = Display fields)
Read Measuring Value Block 3 ->
1 2 3 4
- Check the specification for intake air temperature sensor (display field 4).
Evaluating Display Group 003:
Checking Wiring
- Switch ignition off.
- Connect VAG 1598/18 test box to ECM wiring harness.
- Disconnect 2-pin connector -1- from Intake Air Temperature (IAT) sensor -G72- -2-.
- Check wiring between test box and 2-pin connector for open circuit according to wiring diagram.
- Terminal 1 and test box socket 36
- Terminal 2 and test box socket 33
Resistance: maximum 1.5 Ohms
- Check wiring between test box and 2-pin connector terminal 2 for short circuit to wire terminal 1 or to vehicle Ground (GND), according to wiring diagram.
- Terminal 2 and test box socket 36
- Terminal 2 and vehicle Ground (GND)
Specification: Infinity Ohms
- Additionally, check both wires for short circuit to battery positive (B+).
Specification: Infinity Ohms
If no malfunction in wiring is detected:
- Measure resistance at IAT sensor -G72- terminals 1 and 2.
Resistance Graph
The diagram applies to Engine Coolant Temperature (ECT) sensor -G62- and Intake Air Temperature IAT) sensor -G72-.
Scale A shows resistance values for temperature range 0° - 50 °C (32 - 122 °F) and scale B shows the values for temperature range 50° - 100 °C (122 - 212 °F).
Examples:
- 30 °C (86 °F) corresponds to a resistance from 1500-2000 Ohms
- 80 °C (176 °F) corresponds to a resistance from 275-375 Ohms
If the specification is not attained:
- Replace IAT sensor -G72-.
Continuation Of Check When Display Ambient Temperature
- Remove IAT sensor (harness connector remains connected).
- Read intake air temperature value in display field 4.
- Spray sensor with a commercially available chilling spray and at the same time observe the temperature value.
- The temperature value must decrease.
If the specification is not attained:
- Replace IAT sensor -G72-.
- Read the readiness code. If DTC memory has been erased, repair must be verified via appropriate display group see Readiness code, creating. Refer to "On-Board Diagnostics II With VAG 1551". Testing and Inspection