Intake Air Temperature (IAT) Sensor, Checking
Intake Air Temperature (IAT) sensor, checking
Required special tools and test equipment
- VAG 1551 or VAG 1552 Scan Tool (ST) with VAG 1551/3 adapter cable
- VAG 1598/22 test box
- Multimeter US 1119 (Fluke 83 or equivalent)
- VW 1594 connector test kit
- Wiring diagram
- Chilling spray (commercially available)
Checking
- Connect VAG 1551 or VAG 1552 scan tool and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (with ignition switched on).[1][2]Scan Tool Connecting and Initial Checks
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 -4- to input display group number 4 (004), and press -Q- button to confirm input.
Indicated on display (1-4 = display fields)
Read Measuring Value Block 4 ->
1 2 3 4
- Compare displayed value with specified value for intake air temperature (display field 4):
Display Group 4:
Evaluation of display group 4, display field 4
Display Group 4:
Wiring, checking:
- Switch ignition off.
- Connect VAG 1598/22 test box to ECM harness connector.Connecting VAG 1598/22 Test Box
- Disconnect 2-pin connector from Intake Air Temperature (IAT) sensor -G42-.
- Check wiring for open circuit, between ECM/test box and 2-pin IAT harness connector (to ECM).
- Connector terminal 1 to ECM/test box socket 54
- Connector terminal 2 to ECM/test box socket 67
- Specified value: max. 1.5 Ohms
- Check wiring for short circuit between ECM/test box and 2-pin harness connector according to wiring diagram.
- Connector terminal 1 to vehicle Ground
- Connector terminal 1 to ECM/test box socket 67
- Connector terminal 1 to terminal 2
- Specified value: Infinity Ohms
- Check wiring between ECM and 2-pin harness connector for short circuit to battery B+.
Specified value: 0 volts
If wiring is OK:
- Check resistance across terminals of IAT sensor -G42-.
Specified value at approx. 20° C (68° F): approx. 1.5-3.5 k Ohms
If resistance is NOT OK:
- Replace intake air temperature sensor -G42-.
(when IAT sensor indicates approx. ambient temperature)
- Without disconnecting harness connector, remove IAT sensor -G42-.
- Monitor intake air temperature value in display field 4.
- Spray sensor with commercially available chilling spray and check temperature value in display field 4.
- Temperature value must decrease.
If NOT:
- Replace intake air temperature sensor -G42-.
- Check readiness code.If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code.
Readiness Code Reading
Readiness Code, Generating