Intake Air Temperature (IAT) Sensor, Checking

Intake Air Temperature (IAT) Sensor 2, Checking (Vehicles With Engine Code BKF, BNU)

Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram
- Chilling spray (commercially available)

Test requirements







- The respective fuses of Motronic Engine Control Module (ECM) -J220- must be OK.
- Parking brake must be engaged or else day time driving lights will be switched on.
- Ground (GND) connections between engine and chassis must be OK.
- For vehicles with automatic transmission, selector lever must be in -P-.

Function test
- Connect diagnostic tester.
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 15: Intake air temperature".
- Check specified value of intake air temperature:







If specified value is not obtained:
- Continue test according to the following table:







If specified value is obtained:
- Remember the intake air temperature value.







- Disconnect 2-pin connector from Intake Air Temperature (IAT) Sensor 2 -G299- (arrow).







- Remove Intake Air Temperature (IAT) Sensor 2 -G299-. Re-connect connector.
- Spray sensor with commercially available chilling spray while observing the temperature value. The temperature must decrease.
- End diagnosis and switch ignition off.

If the intake air temperature does not drop:
- Replace Intake Air Temperature (IAT) Sensor 2 -G299-.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

Continuation of test if indication is approx. -40 degrees C:







- Disconnect 2-pin connector from Intake Air Temperature (IAT) Sensor 2 -G299- (arrow).







- Bridge terminals 1 + 2 of connector using the respective adapter cables while observing the indication on display.

If indication jumps to approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Replace Intake Air Temperature (IAT) Sensor 2 -G299-.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If indication remains at approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Check wires to control module according to wiring diagram.

Continuation of test if indication is approx. 143 degrees C:







- Disconnect 2-pin connector from Intake Air Temperature (IAT) Sensor 2 -G299- (arrow).

If indication jumps to approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Replace Intake Air Temperature (IAT) Sensor 2 -G299-.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If indication remains at approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Check wires to control module according to wiring diagram.

Check wires to control module
- Connect test box to control module wiring harness. connect test box for wiring test.







- Check wires between test box and 2-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Terminal 1 + socket 109
Terminal 2 + socket 108

Wire resistance: max. 1.5 Ohms

- Check wires for short circuit to each other.

Specified value: Infinite Ohms

- Erase DTC memory of Engine Control Module (ECM). Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If no malfunctions are found in wire:

Checking resistance







- Measure resistance at Intake Air Temperature (IAT) Sensor 2 -G299-.







Range A displays resistance values for the temperature range of 0 to 50 degrees C, range B displays resistance values for the temperature range of 50 to 100 degrees C.

Read-out examples:
- 30 degrees C is in range A and corresponds to a resistance of 1.5 to 2.0 kohms
- 80 degrees C is in range B and corresponds to a resistance of 275 to 375 Ohms

If specified value is not obtained:
- Replace Intake Air Temperature (IAT) Sensor 2 -G299-.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Motronic Engine Control Module (ECM) -J220-.