With Manufacturer's Scan Tool

Intake Air Temperature (IAT) sensor, checking

Special tools and equipment
- VAG1551 or VAG1552 Scan Tool (ST) with VAG1551/3 adapter cable
- VAG1598/22 test box
- Multimeter Us1119 (Fluke 83 or equivalent)
- VW1594 connector test kit
- Wiring diagram
- Chilling spray (commercially available)

NOTE: If the sensor or sensor wiring malfunctions the engine control module operates with a substitute temperature of 25.5 °C (78 °F).


Checking

- Connect VAG1551 or VAG1552 scan tool and press buttons -0- and -1 - to insert "Engine Electronics" address word 01 (with ignition switched; engine not running. [1][2][3][4]Connecting VAG 1551 Scan Tool

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 display with specified value for intake air temperature sensor (display field 4):

Display Group 4:

Evaluation of display group 4, display field 4





Continuation of check when display reads approx. -46 °C




- Disconnect harness connector -1- from Intake Air Temperature (IAT) sensor -2-.
- Bridge harness connector terminals using adapter cables from Vw1594 connector test kit and observe display.

When display is approx. 141 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Replace Intake Air Temperature (IAT) sensor -G42-.

When display is approx. -46 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output11 function 06, and press -0- button to confirm input.
- Switch ignition off.
- Check wiring using appropriate wiring diagram.


Continuation of check when display reads approx. 141 °C




- Disconnect harness connector -1- from Intake Air Temperature (IAT) sensor -2-.

When display is approx. -46 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Replace Intake Air Temperature (IAT) sensor -G42-.

When display is approx. 141 °C:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Check wiring using appropriate wiring diagram.


Continuation of check when display reads ambient temperature




- Remove Intake Air Temperature (IAT) sensor (arrow). Attach harness connector again.
- Note intake air temperature value in display field 4.
- Spray sender with commercial chilling agent while observing temperature value.
Temperature value must decrease.

If temperature value does not decrease:
- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
- Switch ignition off.
- Check wiring using appropriate wiring diagram.


Wiring, checking




- Connect VAG1598/22 test box to ECM harness connector.




- Disconnect 2-pin connector -1- from Intake Air Temperature (IAT) sensor -2-.
- Check wire between test box socket 67 and 2 pin connector terminal 2 for open circuit using wiring diagram.
- Specified value: max. 1.5 Ohms
- Check wire between test box socket 54 and 2 pin connector terminal 1 for open circuit using wiring diagram.
- Specified value: max. 1.5 Ohms
- Check wiring between ECM and 2-pin harness connector for short circuit to battery B+.
- Specified value: Infinity Ohms

If wiring is OK:



- Check IAT sensor resistance across terminal 1 (signal) and terminal 2 (Ground).




The graph is divided into two temperature ranges:
- Range A: 0-50 °C (32-122 °F)
- Range B: 50-105 °C (122-221 °F)

Examples:
- 30 °C (86 °F) is in range A and corresponds to a resistance of 1.5-2.0 k Ohms
- 80 °C (176 °F) is in range B and corresponds to a resistance of 275-375 Ohms

If resistance is NOT OK:
- Replace Intake Air Temperature (IAT) sensor - G42-.
- Check readiness code. If Diagnostic Trouble Code (DTC) memory has been erased, or ECM was disconnected, generate new readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If the wiring is OK and the resistance measurement values are OK.:
- Replace Motronic ECM -J220-. Service and Repair