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
Heated steering wheel/seat
heaters/seat ventilators
Heated steering wheel
Warm up the grip of the steering
wheel
Seat heaters
Warm up the seat upholstery
Seat ventilators
Maintain good ventilation by
pulling air through the seat
upholstery
WARNING
â– To prevent minor burn injuries
Care should be taken if anyone in
the following categories ...
On-vehicle inspection
Notice:
Perform the maf meter inspection according to the
procedures below.
Only replace the maf meter when both the long
ft#1 value and maf value in the data list (with the
engine stopped) are not within the normal operating
range.
Inspect mass air flow meter
Perform c ...
Stop light switch circuit
Description
While driving with the cruise control, if the ecm detects that the brake
pedal is depressed, the cruise
control operation will be canceled. The stop light switch sends brake pedal
status signals to the ecm.
When the brake pedal is not depressed, terminal st1- is equal to the ...