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DTC P0112: Intake Air Temperature Circuit Low Input (sensor 1)
 
 
 
 
CIRCUIT OPERATION
  • Approximately 5 volts are applied to the intake air temperature sensor 1 output terminal from the ECM terminal ATS via the resistor in the ECM. The ground terminal is grounded with ECM terminal AFSE.
  • The intake air temperature sensor 1 is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases.
  • The intake air temperature sensor 1 output voltage increases when the resistance increases and decreases when the resistance decreases.
 
 
TECHNICAL DESCRIPTION
  • The intake air temperature sensor 1 converts the intake air temperature to a voltage.
  • The ECM checks whether this voltage is within a specified range.
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Intake air temperature sensor 1 output voltage is out of specified range.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
 
 
Check Condition
  • More than 2 seconds have passed since the engine starting sequence was completed.
Judgment Criterion
  • Intake air temperature sensor 1 output voltage is less than 0.2 volt [corresponding to an intake air temperature of 115°C (239°F) or more] for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Using the intake air temperature measured by the intake air temperature sensor 2, carry out the control.
  • Control as if the intake air temperature is 25°C (77°F) if intake air temperature sensor 2 fails.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
  • Intake air temperature sensor 1 failed.
  • Shorted intake air temperature sensor 1 circuit, or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), check data list item 5: Intake Air Temperature Sensor 1.
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool (M.U.T.-IIISE) to the data reading mode for item 5, Intake Air Temperature Sensor 1.
  • The intake air temperature and temperature shown with the scan tool should approximately match.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Go to Step 2.
 
STEP 2. Check the intake air temperature sensor 1.
Refer to Intake Air Temperature Sensor Check .
Is the measured resistance at the standard value?
Go to Step 3.
Replace the mass airflow sensor. Then go to Step 5.
 
STEP 3. Measure the sensor supply voltage at mass airflow sensor harness side connector.
(1) Disconnect the mass airflow sensor connector and measure at the harness side.
(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal ATS line and ground.
  • Voltage should be between 4.5 and 4.9 volts.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the measured voltage between 4.5 and 4.9 volts?
Go to Step 5.
Go to Step 4.
 
STEP 4. Check of short circuit to ground in ATS line between mass airflow sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 5.
Repair the connector(s) or wiring harness. Then go to Step 6.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check data list item 5: Intake Air Temperature Sensor 1.
(1) Turn the ignition switch to the "ON" position.
(2) Set scan tool (M.U.T.-IIISE) to the data reading mode for item 5, Intake Air Temperature Sensor 1.
  • The intake air temperature and temperature shown with the scan tool should approximately match.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
Replace the ECM (Refer to Removal and Installation ). Then go to Step 6.
 
STEP 6. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0112 set?
Retry the troubleshooting.
The inspection is complete.