OPERATION
- A power voltage of 5 V is applied to the intake air temperature sensor output terminal (terminal No. 6) of the air flow sensor connector from the engine-A/T-ECU (terminal No. 64)
- The power voltage is earthed to the engine-A/T-ECU (terminal No. 16) from the air flow sensor (terminal No. 5).
FUNCTION
- The intake air temperature sensor converts the intake air temperature into a voltage and inputs the voltage signal to the engine-A/T-ECU.
- In response to the signal, the engine-A/T-ECU corrects the fuel injection amount, etc.
- The intake air temperature sensor is a kind of resistor, which has characteristics to reduce its resistance as the intake air temperature rises. Therefore, the sensor output voltage varies with the intake air temperature, and becomes lower as the intake air temperature rises.
TROUBLE JUDGMENT
Check Condition
- Excluding 60 seconds after the ignition switch has been in "ON" position or just after the engine has started up.
Judgment Criteria
- A sensor output voltage of 4.6 V or more (intake air temperature below
-40°C or equivalent) for 4 seconds.
- A sensor output voltage of 0.2 V or less (intake air temperature above
120°C or equivalent) for 4 seconds.
PROBABLE CAUSE
- Failed intake air temperature sensor
- Open/short circuit in intake air temperature sensor circuit or loose connector contact
- Failed engine-A/T-ECU
)
Q: Is the check result normal?
YES:
Go to Step 3 
.NO: Repair.
- Disconnect connector, and measure at harness side.
- Voltage between terminal No. 5 and earth.
OK: 2 Ω
or less
Q: Is the check result normal?
YES:
Go to Step 8 .NO: Go to Step 5
.)
)
Q: Is the check result normal?
YES:
Go to Step 6 .NO: Repair.
NOTE: Before checking harness, check intermediate connector C-16, and repair if necessary.
- Check earthing line for open circuit and damage.
Q: Is the check result normal?
YES:
Go to Step 7 .NO: Repair.
STEP 7. MUT-II/III data list
- Item 13: Intake air temperature sensor
OK: At ambient temperature (atmospheric temperature) or equivalent.
Q: Is the check result normal?
YES:
Intermittent malfunction (Refer to GROUP 00 -
How to Use Troubleshooting/Inspection
Service Points 
).NO: Replace engine-A/T-ECU.
- Disconnect connector, and measure at harness side.
- Ignition switch: ON
- Voltage between terminal No. 6 and earth.
OK: 4.5 -
4.9 V
Q: Is the check result normal?
YES:
Go to Step 13 .NO: Go to Step 9
.)
)
- Measure engine-A/T-ECU terminal voltage.
- Disconnect B-08 air flow sensor connector.
- Ignition switch: ON
- Voltage between terminal No. 64 and earth.
OK: 4.5 -
4.9 V
Q: Is the check result normal?
YES:
Go to Step 10 .NO: Go to Step 11
.
Q: Is the check result normal?
YES:
- Check and repair harness between B-08 (terminal No. 6) air flow sensor connector and C-111 (terminal No. 64) engine-A/T-ECU connector.
- Check output line for open circuit.
Q: Is the check result normal?
YES:
Go to Step 12 .NO: Repair.
- Check output line for short circuit.
Q: Is the check result normal?
YES:
Go to Step 7 .NO: Repair.
- Use special tool test harness (MB991709) to connect only terminal No. 5 and No. 6, and then measure at pick-up harness.
- Ignition switch: ON
- Voltage between terminal No. 6 and earth.
OK:
- Ambient temperature at
-20°C : 3.8 - 4.4 V
- Ambient temperature at
0°C : 3.2 - 3.8 V
- Ambient temperature at
20°C : 2.3 - 2.9 V
- Ambient temperature at
40°C : 1.5 - 2.1 V
- Ambient temperature at
60°C : 0.8 - 1.4 V
- Ambient temperature at
80°C : 0.4 - 1.0 V
Q: Is the check result normal?
YES:
Go to Step 7 .NO: Go to Step 14
.
Q: Is the check result normal?
YES:
Go to Step 15 .NO: Repair.
- Check output line for damage.
Q: Is the check result normal?
YES:
Go to Step 16 .NO: Repair.
Q: Is the check result normal?
YES:
- Check intermediate connector C-16, and repair if necessary. If intermediate connector is normal, check and repair harness between B-08 (terminal No. 5) air flow sensor connector and C-127 (terminal No. 16) engine-A/T-ECU connector.
- Check earthing line for damage.