With Manufacturer's Scan Tool

Intake Air Temperature (IAT) Sensor, Checking

NOTE: Only gold-plated contacts may be used to repair the terminals in the IAT sensor.

Special tools and equipment
- V.A.G 1551/1552 Scan tool with adapter cable VAG 1551/3
- Test box VAG 1598/22 (through my 1999)
- Test box VAG 1598/31 (from my 2000)
- Digital multimeter US1119 (Fluke 83 or equivalent)
- Adapter set VAG 1594
- Wiring diagram

Test sequence
- Connect VAG 1551/1552 (Connecting scan tool and selecting engine electronics control module.) Testing and Inspection
- Run engine at idle speed and press buttons - 0- and -1- to select "Engine electronics" address word 01.

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read measured value block" function 08 and confirm entry with -Q- button.

Indicated on display

Read measured value block HELP
Input display group number XXX

- Press buttons -0-, -0- and -7- to select "Display group number 7" and confirm entry with -Q- button.

Indicated on display

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

- Check intake air temperature value in display field 3.
- The temperature value must be approx. ambient temperature.

If a malfunction is present, a constant 136.8 °C will be displayed for the intake air temperature.
- Press -> button
- Press buttons -0- and -6- to select "End output" function 06 and confirm entry with -Q- button.
- Switch ignition off.

If display in field 3 appears unrealistic or a substitute temperature of 136.8 °C is displayed, check IAT sensor and wiring as follows:






- Disconnect 4-pin connector from Manifold Absolute Pressure (MAP) Sensor -G71- with IAT Sensor -G72- (arrow)






- Measure resistance between sensor terminals 1 + 2






- Specification: correlate resistance measurement with chart

NOTE: Scale A shows resistance values for temperature range 0 to 50 °C and scale B shows the values for temperature range 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 the specification is not obtained:
- Replace MAP sensor -G71- together with IAT sensor -G72-.
- Check DTC memory and, if necessary, repair any malfunctions and then erase, Testing and Inspection
- Read readiness code.

If the DTC memory has been erased or the engine control module was disconnected from permanent battery positive (B+), the readiness code must be generated again.

If the specification is obtained:
- Remove wiper arms and plenum cover.






- Connect test box VAG 1598/22 (through my 1999) or VAG 1598/31 (from my 2000) to control module wiring harness.










- Check wiring between test box and connector for open circuit according to wiring diagram.
- Wire resistance: max. 1.5 ohms
- Additionally check wires for short to one another, to vehicle Ground and to battery positive (B+).
- Specification: Infinity ohms

If wiring and the resistance measurement values are OK:
- Replace engine control module.