What it means
Voltage on the AFCM power relay control line is below the expected window. Wire shorted to ground or coil short.
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 AFCM power relay supplies the alternative-fuel control module when commanded. The engine control module monitors the relay control-line voltage and sets P2A33 when it falls below the expected range, such as from a short to ground or a relay-coil fault.
Common causes
Most likely first.
- Control wire shorted to ground
- Internal short in relay coil
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Alternative-fuel system warning light
- Alternative-fuel mode unavailable
How to diagnose it
- Save freeze-frame data and check relay-command and AFCM status to see whether the low reading occurred while the relay was being switched.
- Inspect the AFCM relay socket and control-wire harness for chafing to ground, moisture, corrosion, or loose terminals.
- Check the relay coil and socket connections for a short or poor contact, using the manufacturer's test procedure.
- With the relay disconnected as directed by the manufacturer, test the control wire for an unintended connection to ground.
- If the wire and relay pass, check module command and connector terminal condition against the manufacturer's circuit procedure.
Common fixes
- Clean and secure corroded or loose relay-socket terminals.
- Repair control-wire insulation damaged where it contacts ground.
- Replace the AFCM power relay if its coil is internally shorted.
- Repair a confirmed module connector or control-output fault.
Can I keep driving?
Alternative-fuel mode may be unavailable, and the vehicle may use another available fuel mode. Avoid relying on the alternative-fuel system until repaired; stop if the vehicle has no usable fuel mode or develops drivability problems.
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.