What it means
The control module detects high voltage 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 bank 2 intake air oxygen sensor uses a reference voltage circuit to provide readings the control module can interpret. P2AC6 sets when that circuit voltage is higher than expected, which can be caused by contact with battery voltage, an overvoltage supply or a faulty connection.
Common causes
Most likely first.
- Reference wire shorted to B+
- Sensor reference regulator overvoltage
- Connector pins corroded - high contact resistance
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 data with bank 1, if fitted, to establish when the high-voltage fault appears.
- Inspect bank 2 reference wiring for chafing or contact with a power feed and check its connector for corrosion or loose pins.
- Measure the reference voltage at the bank 2 sensor connector using the manufacturer's procedure to verify it is above range.
- With the circuit isolated as specified, test the bank 2 reference wire for a short to battery voltage and inspect nearby wiring for cross-contact.
- If the harness passes, test the bank 2 sensor and reference supply circuit for an internal fault or overvoltage source.
Common fixes
- Repair a bank 2 reference wire shorted to battery voltage.
- Clean or repair corroded or loose bank 2 connector terminals.
- Reroute or secure harness sections contacting a power feed.
- Replace the bank 2 sensor or repair its reference supply only if testing confirms it is the source of excess voltage.
Can I keep driving?
You can generally drive gently if the engine runs normally, but fuel consumption may increase and emissions testing may be affected. Limit driving if the engine begins to hesitate or run roughly.
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.