Actron CP9087 - Manual (Page 11)

2-3
Air TEMPERATURE
What to
Inspect
Sensor operation (see test on page 2-4). Poor
connections at sensor or computer. Faulty sensor
wiring (open or short circuits). Heavy deposits on
sensor tip which can cause poor response.
Restricted or blocked air passageways.
Engine running too hot (problems with
antifreeze, thermostat, water pump, fan, belts,
low engine oil).
When to Test
• Related trouble codes sent by computer.
• Driveability problems such as hard starting,
rough idle, stalling, hesitation, stumble, surging,
poor fuel economy, or black exhaust smoke.
Location
The sensor is threaded into the intake manifold,
throttle body, rear of air cleaner assembly or
elsewhere along the path of air entering the
engine. Sometimes this sensor is built into a vane
airflow meter or mass airflow sensor assembly.
One connector handles both the air flow and
temperature sensor circuits.
How is It
Used?
The computer needs to know air temperature to
calculate the amount of air entering the engine.
Then, the computer can provide the proper air/fuel
mixture for the desired operating condition.
HIGH
SENSOR
RESISTANCE
LOW
Cold Hot
TEMPERATURE
What is It?
The air temperature sensor is a thermistor - a
resister whose resistance changes with temperature.
The hotter the sensor gets, the lower the resistance
becomes. The thermistor is mounted inside the tip of
a threaded metal housing. This is a 2-wire sensor.
Typical Air Temperature Sensor