P00AC IAT Sensor 1 Circuit Low Input Bank 2
OBD-II Trouble Code Technical Description
Intake Air Temperature Sensor 1 Circuit Low Input Bank 2
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Although generic, the specific repair steps may vary depending on make/model.
The IAT (intake air temperature) sensor simply measures the temperature of air that is entering the engine. Intake air temperature is important because the higher the intake air, the higher the combustion temperatures. High combustion temperatures result in increased Nox (Nitrogen oxides) emissions.
To keep these higher temps from causing increased combustion temps, the intake air tubing should be intact, allowing the engine to "breathe" air that isn't sampled from the engine compartment. The IAT sensor measures air temp by using a thermistor, or a thermometer of sorts. The thermistor is supplied 5 volts reference voltage from the PCM (powertrain control module) and a ground. Usually, when the air temperature is cold the resistance in the thermistor is high and when the air temperature is warmer, the resistance decreases.
This change in resistance changes the 5 V reference from the PCM, thereby informing the PCM of the temperature of incoming air. If the PCM notices that the incoming bank 2 air temp sensor is unusually high, say, 300 degrees, when the engine temp is still relatively low, it will set a P00AC. Bank 2 is the side of the engine that does not contain cylinder #1.
Related Bank 2 IAT sensor circuit trouble codes:
- P00AA Intake Air Temperature Sensor 1 Circuit Bank 2
- P00AB Intake Air Temperature Sensor 1 Circuit Range/Performance Bank 2
- P00AD Intake Air Temperature Sensor 1 Circuit High Bank 2
- P00AE Intake Air Temperature Sensor 1 Circuit Intermittent/Erratic Bank 2
There may be no noticeable symptoms of a P00AC code other than an MIL (Malfunction Indicator Lamp). However, a emissions test may reveal higher Nox readings depending on the type of IAT failure. Or the engine may ping under load, depending on the type of IAT failure.
Usually the P00AC is caused by a bad bank 2 IAT sensor (internally shorted or open or otherwise damaged), but it could also be:
- No reference voltage to the bank 2 IAT sensor due to an open wire
- Excessively high intake air temperatures
- Short to ground on signal circuit
- Damaged IAT connector
- Bad PCM
Hook up your scan tool or code reader and read the IAT reading. With a cold engine, the IAT should roughly match the coolant reading, since both will read ambient temperature. If the IAT #2 is reading excessively high, check the IAT connector for damage. If you find none, unplug the IAT sensor and recheck the reading. It should now read the minimum, around -20 deg. If it does, then replace the IAT sensor #2.
But, if the reading is still high, unplug the sensor and check for resistance across the two wiring harness terminals. If there is infinite resistance, then the PCM itself is bad. If the resistance isn't infinite, then check and repair the short to ground on the signal circuit.
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