What it means
The sense feedback voltage from the AFCM power relay is below the expected window. Indicates the relay output stays low when the relay is commanded on.
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, while its sense line reports the relay's switched output. The module sets P2A36 when the sense voltage stays below the expected range, indicating that output is not appearing when the relay is commanded on.
Common causes
Most likely first.
- Relay contact stays open
- Feedback wire shorted to ground
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Alternative-fuel system warning light
- Alternative-fuel mode unavailable
How to diagnose it
- Capture freeze-frame and live relay-command and sense data to confirm the relay was commanded on while feedback remained low.
- Inspect the relay socket, sense-wire connector, and harness for corrosion, loose or pushed-back pins, and damage.
- Check relay output at the specified test points while commanded on, following the manufacturer's procedure.
- Test the sense wire for an open or short to ground, and check connector contact resistance against the manufacturer's specification.
- If relay output and wiring are correct, verify the module's sense input and command circuit using the manufacturer's diagnostic procedure.
Common fixes
- Clean or repair corroded relay-socket or sense-line terminals.
- Repair an open or grounded sense wire.
- Replace the AFCM power relay if its contacts fail to close or carry output.
- Repair a confirmed module feedback-input fault.
Can I keep driving?
The AFCM may disable alternative-fuel operation because relay power is not confirmed. Use another available fuel mode if the vehicle runs normally, and do not depend on alternative fuel until the low-feedback fault is fixed.
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.