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DTC P0112: Intake Air Temperature Circuit Low Input
 
 
 
 
CIRCUIT OPERATION
  • Approximately 5 volts are applied to the intake air temperature sensor 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 is a negative temperature coefficient type of resistor. When the intake air temperature rises, the resistance decreases.
  • The intake air temperature sensor output voltage increases when the resistance increases and decreases when the resistance decreases.
 
 
TECHNICAL DESCRIPTION
  • The intake air temperature sensor 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 output voltage is out of specified range.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored 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 two seconds have passed since the engine starting sequence was completed.
Judgment Criterion
  • Intake air temperature sensor output voltage is less than 0.2 volt [corresponding to an intake air temperature of 115°C (239°F) or more] for two seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
Control as if the intake air temperature is 25°C (77°F).
 
 
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function, OBD-II Drive Cycle - Pattern 22 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be stored are:)
  • Intake air temperature sensor failed.
  • Shorted intake air temperature sensor circuit, or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Using scan tool (M.U.T.-III), check data list item 5: Intake Air Temperature Sensor.
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T.-III) (Refer to ).
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool (M.U.T.-III) to the data list mode for item 5, Intake Air Temperature Sensor.
  • The intake air temperature and temperature shown with the scan tool (M.U.T.-III) 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.
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. Check of short circuit to ground in ATS line between intake air temperature sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 4.
Repair the connector(s) or wiring harness. Then go to Step 5.
 
STEP 4. Using scan tool (M.U.T.-III), check data list item 5: Intake Air Temperature Sensor.
(1) Turn the ignition switch to the "ON" position.
(2) Set scan tool (M.U.T.-III) to the data list mode for item 5: Intake Air Temperature Sensor.
  • The intake air temperature and temperature shown with the scan tool (M.U.T.-III) 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 ). Then go to Step 5 .
 
STEP 5. 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 22 ).
(2) Check the DTC.
Is DTC P0112 stored?
Retry the troubleshooting.
The inspection is complete.