Intake Air Temperature (IAT) Sensor, Checking
Intake Air Temperature (IAT) Sensor, Checking
NOTE:
- When servicing terminals in the harness connector for the Mass Air Flow (MAF) sensor or the Intake Air Temperature (IAT) sensor, use only gold-plated terminals.
- The Intake Air Temperature (IAT) sensor -G42- is a component of the Mass Air Flow (MAF) sensor -G70- and cannot be replaced individually.
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)
Requirements
- The respective fuses of Motronic Engine Control Module (ECM) -J220- must be OK.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in position -P- or -N-.
Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select 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:
- Remove intake air hose between Mass Air Flow (MAF) sensor and throttle valve control module.
- Remember the intake air temperature value.
- Spray sensor (arrow) with commercially available chilling spray and watch the temperature value. The temperature must decrease.
- End diagnosis and switch ignition off.
If the intake air temperature does not drop:
- Replace Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes.
Continuation of test if indication is approx. -40 or -46 degrees C
- Disconnect 5-pin connector from Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42- (arrow).
- Bridge terminals 1 + 3 of connector using the respective adapter cables while observing the indication on display.
If indication jumps to approx. 140 degrees C.
- End diagnosis and switch ignition off.
- Replace Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes.
If indication remains at approx -40 or -46 degrees C.
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.
Continuation of test if indication is approx. 140 degrees C
- Disconnect 5-pin connector from Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42- (arrow).
If indication jumps to approx -40 or -46 degrees C.
- End diagnosis and switch ignition off.
- Replace Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes.
If indication remains at approx. 140 degrees C.
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.
Checking wiring
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test
Vehicles with engine code AEG
- Check wires between test box and 5-pin connector for open circuit according to wiring diagram.
Terminal 1 + socket 40
Terminal 3 + socket 12
Wire resistance: max. 1.5 Ohms
Vehicles with engine code AVH, AZG, BBW, BEV
- Check wires between test box and 5-pin connector for open circuit according to wiring diagram.
Terminal 1 + socket 26
Terminal 3 + socket 27
Wire resistance: max. 1.5 Ohms
Continued for all vehicles
- Check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinite Ohms
If no malfunctions are found in wire:
- Measure resistance at Intake Air Temperature (IAT) sensor -G42-, terminals 1 (signal) and 3 (Ground).
Range A displays resistance values for temperature range of 0 to 50 degrees C, range B displays resistance values for 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 kilo Ohms
- 80 degrees C is in range B and corresponds to a resistance of 275 to 375 Ohms
If specified value is not obtained:
- Replace Mass Air Flow (MAF) sensor -G70- with Intake Air Temperature (IAT) sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes.
If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Motronic Engine Control Module (ECM) -J220-.