Intake Air Temperature Sensor, Checking

Diagnostic Procedures

Intake Air Temperature Sensor, Checking

• Cylinder bank 1 is located in direction of travel, right.

• Cylinder bank 2 is located in direction of travel, left.

• Use only gold-plated terminals when servicing terminals in harness connector.

Special tools, testers and auxiliary items required

• Multimeter (VAG1526) or Multimeter (VAG1715)

• Connector test kit (VAG1594)

• Wiring diagram

• Chilling spray (commercially available)

Test Prerequisites

• Fuses in E-box (plenum chamber, left) must be OK:

• Battery voltage must be at least 11.5 volts.

• All electrical consumers such as, for example, lights and rear window defroster must be switched off.

• For vehicles with automatic transmission, selector lever must be in P.

• If vehicle is equipped with an A/C system, it must be switched off.

• Ground (GND) connections between engine and chassis must be OK.

Cylinder bank 1: Check Intake Air Temperature (IAT) Sensor (G42).

Cylinder bank 2: Intake Air Temperature (IAT) Sensor 2 (G299).

Intake Air Temperature Sensor 2 (G42) Test Sequence

- 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 a temperature is indicated which is below the ambient temperature of sensor, first check sensor wires for contact resistance. Note that while the vehicle is standing still the sensor might warm up due to radiant heat.

If a substitute value of approx. 134° C is displayed:

- Check resistance at Intake Air Temperature (IAT) Sensor (G42).

If specified value is not obtained:

- Check Intake Air Temperature (IAT) Sensor (G42).

Sensor, Checking

- Remove Intake Air Temperature (IAT) Sensor (G42) with Charge Air Pressure Sensor (G31) (- A -).

- Reconnect harness connector to sensor.

- Remember the intake air temperature value.

- Spray the 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 (G42) with Charge Air Pressure Sensor (G31).

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

Sensor, Checking Resistance

- Measure resistance at Intake Air Temperature (IAT) Sensor (G42) terminals 1 + 2.

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

Read-out examples:

• 30°C is in range A and corresponds to a resistance of 1.5 to 2.0 kohms

• 80°C is in range B and corresponds to a resistance of 275 to 375ohms

If specified value is not obtained:

- Replace Intake Air Temperature (IAT) Sensor (G42) with Charge Air Pressure Sensor (G31).

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

If specified value is obtained:

- Connect test box ((VAG1598/42)) to Engine Control Module (ECM) (J623) wiring harness using adapter cable ((VAG1598/39-2)) , connecting test box for wiring test.

- Check wires between test box and 4-pin connector for open circuit according to wiring diagram.

Terminal 1+socket 76

Terminal 2+socket 38

Wire resistance: max. 1.5 ohms

- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specified value: infinite ohms

If no malfunctions are detected in the wires and the resistance values are OK:

- Replace Engine Control Module (ECM) (J623) --> [ Engine Control Modules, Replacing ] Engine Control Modules, Replacing.

Intake Air Temperature Sensor 2 (G299) Test Sequence

- 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 a temperature is indicated which is below the ambient temperature of sensor, first check sensor wires for contact resistance. Note that while the vehicle is standing still the sensor might warm up due to radiant heat.

If a substitute value of approx. 134°C is displayed:

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

If specified value is not obtained:

- Check Intake Air Temperature (IAT) Sensor 2 (G299).

Sensor, Checking

- Remove Intake Air Temperature (IAT) Sensor 2 (G299) with Charge Air Pressure Sensor 2 (G447) (- B -).

- Reconnect harness connector to sensor.

- Remember the intake air temperature value.

- Spray the 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) with Charge Air Pressure Sensor 2 (G447)

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

Sensor, Checking Resistance

- Measure resistance at Intake Air Temperature (IAT) Sensor 2 (G299) terminals 1 + 2.

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

Read-out examples:

• 30°C is in range A and corresponds to a resistance of 1.5 to 2.0 kohms

• 80°C is in range B and corresponds to a resistance of 275 to 375ohms

If specified value is not obtained:

- Replace Intake Air Temperature (IAT) Sensor 2 (G299) with Charge Air Pressure Sensor 2 (G447).

- Erase DTC memory of Engine Control Module (ECM) --> [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

- Generate readiness code --> [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

If specified value is obtained:

- Connect test box ((VAG1598/42)) to Engine Control Module 2 (J624) wiring harness using adapter cable ((VAG1598/39-2)) , connecting test box for wiring test.

- Check wires between test box and 4-pin connector for open circuit according to wiring diagram.