Signal Circuit Inspection

Check reference voltage in harness
1. Ignition "OFF"
2. Disconnect IAT sensor connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage between terminal 5 of IAT sensor harness connector and chassis ground.
  Specification: Approx. 5V
  
  NOTE: In case of short to battery in IATS, Voltage reading can be displayed either 5V or 12V. 5V means that IATS is short to another 5V source such as MAFS power etc. and 12V means that IATS is short to battery voltage source such as Power (12V) etc.
5. Is the measured voltage within specifications?
  YES:
  - Go to "COMPONENT INSPECTION " procedure.
  NO:
  - Go to step 2 "Check for short to ground in harness" as below.
NOTE: Be sure that 5V reading is caused just by Intake Air Temperature Sensor Pull-up voltage not short to another 5V source such as MAFS power.
Check for short to Battery in harness
1. Ignition "OFF"
2. Disconnect IAT sensor connector
3. Measure resistance between terminal "5" and "2" of the IAT sensor harness connector.
4. Measure resistance between terminal "5" and "4" of the IAT sensor harness connector.
  Specification: Infinite
5. Is the measured resistance within specifications?
YES:
- Go to step 3 "Check for open in harness" as below.
NO:
- Check for short to battery in harness.
- Repair or replace as necessary. And then, go to "VERIFICATION OF VEHICLE REPAIR " procedure.
Check for open in harness
1. Ignition "OFF"
2. Disconnect IAT sensor connector and PCM connector.
3. Measure resistance between terminal "5" of the IAT sensor harness connector and "24/C121-B" of the PCM harness connector.
  Specification: Approx. below 1 Ω
4. Is the measured resistance within specifications?
  YES:
  - Go to "GROUND CIRCUIT INSPECTION " procedure.
  NO:
  - Check for open in harness, repair or replace as necessary and then go to "VERIFICATION OF VEHICLE REPAIR " procedure.