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 drivability.
Hint: when any of dtcs p0110, p0112 and p0113 are set, 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 any of these dtcs are set, check the iat by selecting the following menu items on the intelligent tester: diagnosis / enhanced obd ii / data list / primary / 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 sets 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 sets 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 sets dtc p0112.
If the malfunction is not repaired successfully, a dtc is set 0.5 Seconds after the engine is next started.
Monitor strategy
Typical enabling conditions
Typical malfunction thresholds
Component operating range
Wiring diagram
Inspection procedure
Hint:
Read freeze frame data using the intelligent tester. 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.
Result
Standard: same as actual intake air temperature (iat).
Result
Hint:
Standard value: 140°c (284°f) or higher
Standard resistance
Confirm good connection to ecm. If ok, replace ecm
Standard value: -40°c (-40°f)
Standard resistance
Check for short circuit
If the wire harness is ground shorted (fig. 5), Locate
the section by conducting a resistance check with
the body ground (below).
Check the resistance with the body ground.
Disconnect connectors a and c, and measure
the resistance
Standard resistance (fig. 6)
Hint:
Measure ...
Terminals of ecm
Hint:
The standard normal voltage between each pair of ecm
terminals is shown in the table below. The appropriate
conditions for checking each pair of terminals are also
indicated. The result of checks should be compared with the
standard normal voltage for that pair of terminals, displayed ...
Unlocking and locking the doors
Front doors
Grip the driver’s door handle to
unlock the door. Grip the passenger’s
door handle to unlock all the
doors.*
Make sure to touch the sensor on
the back of the handle.
The doors cannot be unlocked for
3 seconds after the doors are
locked.
*: The door unlock settings can be ...