What it means
The control module detects an open or fault in the reference voltage circuit for the intake air oxygen sensor on bank 2. The sensor reading may be unreliable.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The intake air oxygen sensor on bank 2 monitors oxygen in the intake air, and its reference circuit supplies the voltage needed for a dependable signal. P2AC3 sets when the control module detects an open or interrupted reference path for the bank 2 sensor, leaving its reading unreliable or unavailable.
Common causes
Most likely first.
- Open in reference voltage wire
- Intake air O2 sensor failed
- Pin pushed back out of connector body
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Record freeze-frame data and compare bank 2 sensor and fuel-trim readings with bank 1, if fitted, to see when the fault occurs.
- Locate the bank 2 intake air oxygen sensor from service information and inspect its connector for corrosion, damage or a pin pushed back into the housing.
- Check for the specified reference voltage at the bank 2 sensor connector using the manufacturer's circuit procedure.
- If voltage is missing, test the bank 2 reference wire for continuity and inspect its connectors for an open or poor terminal contact.
- If the harness and connector pass, test the bank 2 sensor and module-side circuit before replacing components.
Common fixes
- Reseat a backed-out bank 2 connector pin or repair its terminal.
- Repair an open or damaged bank 2 reference wire.
- Clean or replace corroded bank 2 sensor connector contacts.
- Replace the bank 2 intake air oxygen sensor if testing confirms an internal fault.
Can I keep driving?
You can usually drive gently if the engine runs normally, though fuel use may increase and the vehicle may fail an emissions test. Avoid continued driving if rough running or hesitation develops.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.