SFI SYSTEM, Diagnostic DTC:P0112, P0113

DESCRIPTION

• The intake air temperature sensor, mounted on the mass air flow meter, monitors the intake air temperature. The intake air temperature sensor has a built-in thermistor with a resistance that varies according to the temperature of the intake air. When the intake air temperature is low, the resistance of the thermistor increases. When the temperature is high, the resistance drops. These variations in resistance are transmitted to the ECM as voltage changes (see Fig. 1).

• The intake air temperature sensor is powered by a 5 V supply from the THA terminal of the ECM, via resistor R.

• Resistor R and the intake air temperature sensor are connected in series. When the resistance value of the intake air temperature sensor changes according to changes in the intake air temperature, the voltage at terminal THA also varies. Based on this signal, the ECM increases the fuel injection volume when the engine is cold to improve driveability.

  Tech Tips

  When DTC P0112 or P0113 is stored, the ECM enters fail-safe mode. During fail-safe mode, the intake air temperature is estimated to be 20°C (68°F) by the ECM. The ECM continues operating fail-safe mode until a pass condition is detected.

MONITOR DESCRIPTION

The ECM monitors the sensor voltage and uses this value to calculate the intake air temperature. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a malfunction in the intake air temperature sensor and stores a DTC.

Example:

If the sensor output voltage is higher than 4.91 V for 0.5 seconds or more, the ECM determines that there is an open circuit in the intake air temperature sensor circuit and stores DTC P0113. Conversely, if the output voltage is below 0.18 V for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit and stores DTC P0112.

If the malfunction is not repaired successfully, a DTC is stored 0.5 seconds after the engine is next started.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING INTELLIGENT TESTER (INTAKE AIR TEMPERATURE)

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the tester on.

   4. Enter the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

   5. Read the value displayed on the tester.

      Result

      Result	Proceed to
      -40°C (-40°F)	A
      140°C (284°F) or higher	B
      Same as actual intake air temperature	C

      Tech Tips

      
      

      • If there is an open circuit, the intelligent tester indicates -40°C (-40°F).

      
      

      • If there is a short circuit, the intelligent tester indicates 140°C (284°F) or higher.

   
   

   B

   READ VALUE USING INTELLIGENT TESTER (CHECK FOR SHORT IN WIRE HARNESS) Click here

   C

   CHECK FOR INTERMITTENT PROBLEMS Click here

   A

2. READ VALUE USING INTELLIGENT TESTER (CHECK FOR OPEN IN WIRE HARNESS)

   

   Text in Illustration

   *1	Mass Air Flow Meter
   *2	ECM
   *a	Front view of wire harness connector (to Mass Air Flow Meter)

   
   

   1. Disconnect the mass air flow meter connector.

   2. Connect terminals 1 (THA) and 2 (E2) of the mass air flow meter wire harness side connector.

   3. Connect the intelligent tester to the DLC3.

   4. Turn the ignition switch to ON.

   5. Turn the tester on.

   6. Enter the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

   7. Read the value displayed on the tester.

      Standard value
      140°C (284°F) or higher

   8. Reconnect the mass air flow meter connector.

   
   

   NG

   CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM) Click here

   OK

   CONFIRM GOOD CONNECTION TO SENSOR. IF OK, REPLACE MASS AIR FLOW METER Click here

3. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

   
   

   1. Disconnect the mass air flow meter connector.

   2. Disconnect the ECM connector.

   3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition C33-1 (THA) - C35-15 (THA) Always Below 1 Ω C33-2 (E2) - C35-7 (ETHA) Always Below 1 Ω

   4. Reconnect the mass air flow meter connector.

   5. Reconnect the ECM connector.

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

   CONFIRM GOOD CONNECTION TO ECM. IF OK, REPLACE ECM Click here

4. READ VALUE USING INTELLIGENT TESTER (CHECK FOR SHORT IN WIRE HARNESS)

   

   Text in Illustration

   *1	Mass Air Flow Meter
   *2	ECM

   
   

   1. Disconnect the mass air flow meter connector.

   2. Connect the intelligent tester to the DLC3.

   3. Turn the ignition switch to ON.

   4. Turn the tester on.

   5. Enter the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

   6. Read the value displayed on the tester.

      Standard value
      -40°C (-40°F)

   7. Reconnect the mass air flow meter connector.

   
   

   NG

   CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM) Click here

   OK

   REPLACE MASS AIR FLOW METER Click here

5. CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

   
   

   1. Disconnect the mass air flow meter connector.

   2. Disconnect the ECM connector.

   3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition C33-1 (THA) or C35-15 (THA) - Body ground Always 10 kΩ or higher

   4. Reconnect the mass air flow meter connector.

   5. Reconnect the ECM connector.

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

   REPLACE ECM Click here