75 IAT Unstable
From SaturnWiki
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Description
The air temperature sensor (ATS) is a thermistor located in the air intake passage of the air induction system on the engine. When the sensor is cold it has a high resistance, the resistance decreases as the temperature of the sensor increases. The PCM supplies a five volt signal to the sensor which is also connected to ground. The PCM reads the voltage drop on the sensor signal line to determine air temperature.
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Information Flag Parameters
Information Flag 75 will set if:
- ATS reading changes more than 15°C (59°F) in 100 milliseconds.
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Diagnostic Aids
- When attempting to diagnose an intermittent problem, use the Scan Tool to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem. Select MALF History from Scan Tool EC menu.
- Check the tightness of the female terminal grip with a spare male terminal.
- Wiggle the ATS connector. Watch Scan Tool to see if ATS reading changes falls sharply.
- Check ATS connector. Check for shorted terminals.
- Wiggle and tug the harness. Watch Scan Tool to see if ATS reading rises or drops sharply.
- Wiggle and tug the harness at the PCM. Lightly tap the PCM. Watch for changes in the ATS reading.
- Check the PCM connector. Check for shorted terminals.
NOTICE: Information flags should be used for diagnostic purposes only. They do not necessarily indicate component malfunction/failure.
