Fuel and air

P00AC — Intake Air Temperature Sensor 1 Circuit Low, Bank 2

Severity: low Safe to drive

What P00AC means

The engine control unit feeds the intake air temperature sensor a 5 V reference and reads the voltage drop to work out air temperature. P00AC sets when that signal falls below the expected range, which the ECU interprets as extremely hot air. The usual culprits are a failed sensor or a signal wire shorted to ground. A bank 2 sensor exists on engines with separate intake paths for each cylinder bank, such as V-type and flat engines.

Symptoms

  • Check Engine light on
  • Rough idle
  • Reduced engine performance
  • Increased fuel consumption
  • Hard starting when cold
  • Possible emissions test failure

Possible causes

  1. Failed bank 2 intake air temperature sensor
  2. Signal wire shorted to ground or damaged harness insulation
  3. Moisture or corrosion in the sensor connector
  4. Internal short in the sensor
  5. Fault in the 5 V reference or ground circuit
  6. Faulty ECU (rare)

How to diagnose

  1. Read all codes and freeze frame data, then clear the code and see whether it returns.
  2. Compare the bank 1 and bank 2 intake air temperature readings on a scan tool; on a cold engine both should be close to ambient temperature.
  3. If bank 2 shows an unrealistically high value (such as 250°F / 120°C or more), unplug the sensor: the reading should drop to the open-circuit value.
  4. Inspect the connector and harness for moisture, corrosion, chafing and contact with hot parts.
  5. Measure the sensor resistance and compare it with the specification for your model at a known temperature.
  6. Check the signal wire for a short to ground and confirm 5 V reference at the connector.
  7. If wiring and sensor test fine, evaluate the ECU only after ruling out everything else.

Common fixes

  • Replace the bank 2 intake air temperature sensor
  • Repair the damaged wiring or replace the connector
  • Clean the terminals and eliminate moisture intrusion
  • Fix the reference voltage or ground fault
  • Replace or reprogram the ECU (last resort)

Questions and answers

What does P00AC mean?

It is a low signal in the bank 2 intake air temperature sensor 1 circuit. The ECU thinks the air is extremely hot, but the cause is usually a bad sensor or a short to ground.

Can I drive with code P00AC?

Usually yes, but don't put it off. The ECU relies on backup values, so fuel economy and smoothness may suffer.

How do I tell a bad sensor from a wiring problem?

Unplug the sensor and watch the scan tool. If the reading changes to the open-circuit value, the sensor or its connector is the likely cause. If it doesn't change, look for a short to ground in the harness.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.