OBD Intake Air O2 Sensor Reference Voltage Circuit Low Bank 2
What it means
P2AC5 stands for Intake Air O2 Sensor Reference Voltage Circuit Low Bank 2. P2AC5 is a P code, so the fault sits in the engine, transmission and emissions systems. For P2AC5, work through the cause list below, cheapest checks first.
Where it lives
For P2AC5, the sensor sits on the circuit this code reports. The description of P2AC5 puts it on bank 2.
What to check first
For P2AC5, compare the reading on bank 2 against the other bank on the same scan tool, because a bank that reads differently from its twin is the fault.
Check these first
- P2AC5: Faulty or contaminated sensor in the fuel/air metering circuit
- P2AC5: Damaged or shorted wiring or connector for the affected circuit
- P2AC5: Vacuum leak or intake system restriction
- P2AC5: Failing fuel pump, injector, or fuel pressure regulator
What to do next
P2AC5 reports from the powertrain control system. These steps cover P2AC5 in general, and the exact cause on your vehicle can differ from the cause named above.
- P2AC5: Read freeze frame data and related codes with an OBD-II scanner
- P2AC5: Inspect the affected sensor wiring and connector for damage
- P2AC5: Compare live sensor readings (fuel trim, airflow, temperatures) to manufacturer specs
- P2AC5: Smoke test the intake system if lean or vacuum conditions are suspected
- P2AC5: Replace the failed component after confirming it with live data
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Updated
Generic SAE J2012 definition. Last updated 2026-08-30.