Intake Air Temperature (IAT) Sensor, Checking

Intake Air Temperature (IAT) sensor, checking

Special Tools, Testers And Auxiliary Items:
- VAG 1551/1552 Scan Tool with VAG 1551/3 adaptor cable
- VAG 1598/18 Test Box
- Multimeter (Fluke 83 or equivalent)
- VW 1594 adaptor kit
- Wiring diagram

Test Sequence:
- Connect VAG 1551/1552 Scan Tool
- Start engine and let idle
- Press -0- and -1- buttons to select "Engine Electronics" address word 01
Display will appear as shown:

Rapid data transfer HELP
select function XX

- Press -0- and -8- buttons to select "Read Measuring Value Block" function 08
- Press -Q- button to enter input
Display will appear as shown:

Read measuring value block HELP
Input display group number XXX

- Press -0-, -0- and -7- buttons to select "display group 7"
- Press Q button to enter input
Display will appear as shown:

Read measuring value block 7 ->
15.4°C 15.9°C 16.7°C

If implausible value appears in display field 3 or a substitute temperature of 136.8°C is displayed, check Intake Air Temperature sensor and sensor wiring:
- Press -> button
- Press -0- and -6- buttons to select "End Output" function 06
- Press -Q- button to enter input
- Switch OFF ignition






- Disconnect harness connector -1- from Intake Air Temperature sensor -2-
- Measure resistance between sensor terminals





Specification: refer to diagram for resistance values
Scale A for temperatures 0 to 50°C
Scale B for temperatures 50 to 100°C

Examples:
30°C corresponds to a resistance from 1500 to 2000 Ohms
80°C corresponds to a resistance from 275 to 375 Ohms

If specification not obtained:
- Replace Intake Air Temperature sensor -G72-
- Display the readiness code

If DTC memory was erased:
- Create readiness code again

If specification obtained:






- Connect Test Box VAG 1598/18 to the Diesel DFI ECM connector






- Check wiring for open circuit between Test Box and the connector using wiring diagram:
terminal 1 + test box socket 64
terminal 2 + test box socket 33
Wire resistance: 1.5 Ohms maximum

Also check wires for shorting to one another
Specification: Infinite Ohms

If wiring OK:
- Replace Diesel DFI ECM -J248-
- Display the readiness code

If DTC memory was erased:
- Create readiness code again