Toyota Tundra Service Manual: Intake Air Temperature Circuit Low Input (P0112,P0113)

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.

  HINT:

  When DTC P0112 or 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.

HINT:

When either of these DTCs is stored, check the IAT by entering the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

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 more 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 less than 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.

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

COMPONENT OPERATING RANGE

CONFIRMATION DRIVING PATTERN

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
4. Turn the ignition switch off and wait for at least 30 seconds.
5. Turn the ignition switch to ON and turn the Techstream on.
6. Wait 0.5 seconds or more.
7. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
8. Read the pending DTCs.

   HINT:

   • If a pending DTC is output, the system is malfunctioning.
   • If a pending DTC is not output, perform the following procedure.
9. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
10. Input the DTC: P0112 or P0113.
11. Check the DTC judgment result.

    Tester Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

12. If the test result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

Read freeze frame data using the Techstream. 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

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

(e) Read the value displayed on the Techstream.

Standard:

Same as actual Intake Air Temperature (IAT).

HINT:

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

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

B

GO TO STEP 4

C

CHECK FOR INTERMITTENT PROBLEMS

A

(a) Disconnect the MAF meter connector.

(b) Connect terminals 4 (THA) and 5 (E2) of the MAF meter wire harness side connector.

(c) Connect the Techstream to the DLC3.

(d) Turn the ignition switch to ON.

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

(g) Read the value displayed on the Techstream.

Standard value:

140°C (284°F) or higher

HINT:

Perform "Inspection After Repair" after replacing the mass air flow meter (See page ).

OK

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

NG

(a) Disconnect the MAF meter connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

OK

CONFIRM GOOD CONNECTION TO ECM. IF OK, REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

(a) Disconnect the MAF meter connector.

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to ON.

(d) Turn the Techstream on.

(e) Enter the following menus: Powertrain / Engine and ECT / Data List / Intake Air.

(f) Read the value displayed on the Techstream.

Standard value:

-40°C (-40°F)

HINT:

Perform "Inspection After Repair" after replacing the mass air flow meter (See page ).

OK

REPLACE MASS AIR FLOW METER

NG

(a) Disconnect the MAF meter connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR