What is the P00AC Code?
The P00AC trouble code is a generic powertrain (OBD-II) code that indicates a problem with the Intake Air Temperature (IAT) Sensor 1 Circuit, Bank 2. Specifically, the Powertrain Control Module (PCM) has detected an abnormally low input voltage in this sensor’s circuit.
Role of the IAT Sensor
The IAT sensor measures the temperature of the air entering the engine. This information is crucial for the PCM, which uses it to:
- Adjust the air-fuel mixture.
- Control ignition timing.
- Manage the Exhaust Gas Recirculation (EGR) rate.
- Prevent overheating and excessive Nitrogen Oxide (NOx) emissions.
The sensor operates with a thermistor: its electrical resistance changes with temperature. The PCM sends a 5V reference voltage and measures the returned voltage to determine the temperature.
Related Codes
- P00AA: IAT Sensor 1 Circuit, Bank 2
- P00AB: IAT Sensor 1 Circuit Range/Performance, Bank 2
- P00AD: IAT Sensor 1 Circuit High, Bank 2
- P00AE: IAT Sensor 1 Circuit Intermittent, Bank 2
Symptoms of the P00AC Code
Symptoms can be subtle but often include:
- Illumination of the Malfunction Indicator Lamp (MIL).
- Decreased engine performance or engine hesitation.
- Increased fuel consumption.
- Failure of emissions tests (high NOx emissions).
- Hard starting in cold weather.
Possible Causes of the P00AC Fault
Several issues can trigger this code:
- Faulty IAT Sensor (most common cause).
- Wiring Problem: open wire, short to ground, or damaged connector in the Bank 2 sensor circuit.
- Loss of the 5V reference voltage or ground.
- Obstructed air intake or excessively high intake temperatures.
- PCM failure (rare).
Diagnosis and Solutions for Resolving P00AC
Here is a step-by-step diagnostic procedure:
1. Visual Inspection
Inspect the IAT sensor connector and wiring on bank 2. Look for signs of corrosion, damage, or loose wires.
2. Live Data Reading
Using an OBD2 scanner, observe the temperature value displayed by the bank 2 IAT sensor. On a cold engine, it should be close to the ambient temperature and the engine coolant temperature sensor reading.
3. Sensor Test
If the reading is abnormally low (e.g., -40°C):
- Disconnect the IAT sensor connector.
- If the reading changes to an even lower value or “open circuit,” the problem is likely in the wiring (short to ground).
- If the reading becomes very high (e.g., +140°C), the sensor itself is most likely faulty and needs to be replaced.
4. Electrical Test
Using a multimeter, check for the presence of the 5V reference voltage and ground at the sensor connector (with the connector disconnected). If either of these is missing, check the wiring back to the PCM.
Conclusion and Call to Action
The P00AC code is often resolved by replacing the faulty Bank 2 IAT sensor. However, checking the wiring beforehand is essential to avoid unnecessary part replacement.
Not comfortable performing these steps yourself? Leave the diagnosis to a professional. Use our online tool to get a personalized quote for your vehicle’s repair.