P0112, P0113

DTC Code	DTC Name
P0112	Intake Air Temperature Circuit Low Input
P0113	Intake Air Temperature Circuit High Input

DESCRIPTION

The Intake Air Temperature (IAT) sensor, mounted on the Mass Air Flow (MAF) meter, monitors the IAT. The IAT sensor has a built-in thermistor with a resistance that varies according to the temperature of the intake air. When the IAT 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 IAT sensor is powered by a 5 V supply from the THA terminal of the ECM, via resistor R.
Resistor R and the IAT sensor are connected in series. When the resistance value of the IAT sensor changes, according to changes in the IAT, 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 any of DTCs P0112 and P0113 is stored, the ECM enters fail-safe mode. During fail-safe mode, the IAT is estimated to be 20°C (68°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

DTC Code	DTC Detection Condition	Trouble Area
P0112	A short in the IAT sensor circuit for 0.5 seconds (1 trip detection logic).	Short in IAT sensor circuit IAT sensor (built into MAF meter) ECM
P0113	An open in the IAT sensor circuit for 0.5 seconds (1 trip detection logic).	Open in IAT sensor circuit IAT sensor (built into MAF meter) ECM

Tech Tips

When any of these DTCs are output, check the IAT by entering the following menus: Powertrain / Engine and ECT / All Data / Intake Air.

Temperature Displayed	Malfunction
-40°C (-40°F)	Open circuit
140°C (284°F) or higher	Short circuit

MONITOR DESCRIPTION

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

Tech Tips

Read freeze frame data using the GTS. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

READ VALUE USING GTS (INTAKE AIR TEMPERATURE)

Connect the GTS to the DLC3.
Turn the engine switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / All Data / Intake Air.

Read the value displayed on the tester.

Standard
Same as actual Intake Air Temperature (IAT).

Result
Temperature Displayed	Proceed to
-40°C (-40°F)	A
140°C (284°F) or higher	B
Same as actual IAT	C

Tech Tips

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

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

B

PERFORM ACTIVE TEST USING GTS (CHECK FOR SHORT IN WIRE HARNESS) Click here

C

CHECK FOR INTERMITTENT PROBLEMS Click here

A

READ VALUE USING GTS (CHECK FOR OPEN IN WIRE HARNESS)
1. Disconnect the C50 Mass Air Flow (MAF) meter connector.
2. Connect terminals 4 (THA) and 5 (E2) of the MAF meter wire harness side connector.
3. Connect the GTS to the DLC3.
4. Turn the engine switch on (IG).
5. Turn the tester on.
6. Enter the following menus: Powertrain / Engine and ECT / All Data / Intake Air.
7. Read the value displayed on the tester.
  
  Standard value
  
  140°C (284°F) or higher
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

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

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

Disconnect the C50 MAF meter connector.
Disconnect the C45 ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
C50-4 (THA) - C45-73 (THA)	Always	Below 1 Ω
C50-5 (E2) - C45-98 (ETHA)	Always	Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

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

PERFORM ACTIVE TEST USING GTS (CHECK FOR SHORT IN WIRE HARNESS)
1. Disconnect the C50 MAF meter connector.
2. Connect the GTS to the DLC3.
3. Turn the engine switch on (IG).
4. Turn the tester on.
5. Enter the following menus: Powertrain / Engine and ECT / All Data / Intake Air.
6. Read the value displayed on the tester.
  
  Standard value
  
  -40°C (-40°F)
NG
CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM) Click here

OK

REPLACE MASS AIR FLOW METER Click here

Standard value
-40°C (-40°F)

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

Disconnect the C50 MAF meter connector.
Disconnect the C45 ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
C50-4 (THA) or C45-73 (THA) - Body ground	Always	10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

REPLACE ECM Click here

SFI SYSTEM, Diagnostic DTC:P0112, P0113