What it means
The control circuit of the alternative fuel return line valve reports a control circuit high condition. Excess fuel return to the tank cannot be commanded as expected.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The alternative-fuel return-line valve controls excess fuel flow back to the tank, and the module monitors the circuit that operates it. P2AA1 sets when that circuit reads higher than expected, so the module may be unable to command the valve correctly.
Common causes
Most likely first.
- Control wire shorted to B+
- Open valve coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine or alternative-fuel system warning light, if equipped
- Reduced power or poor acceleration
- Rough running or stalling
How to diagnose it
- Record freeze-frame data and inspect scan-tool valve commands and related codes to identify the conditions when the high-circuit fault appears.
- Inspect the return-line valve connector and control harness for damage, corrosion, loose pins, or contact with a power source.
- Check connector pin condition and fit, because corrosion or poor contact can interrupt the circuit.
- Test the control wire for a short to battery voltage following the manufacturer's procedure.
- Check the valve coil for an open circuit and compare the measurement with the manufacturer's specification.
Common fixes
- Clean or repair corroded or loose valve connector pins.
- Repair the control wire if it is shorted to battery voltage.
- Replace the return-line valve if its coil is open.
- Clear the code and confirm that the valve follows commands without the high-circuit fault returning.
Can I keep driving?
Limit driving if acceleration is poor or the engine runs roughly, and avoid situations where a stall would be hazardous. If the engine stalls or the fuel-system warning calls for stopping, pull over safely.
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.