What it means
The sense feedback voltage from the AFCM power relay is above the expected window. Indicates relay output is energised when the relay should be off, or wire shorted to B+.
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 switches power to the alternative-fuel control module, and its sense line tells the module whether that output is present. P2A37 sets when the sense voltage is higher than expected, suggesting output remains present with the relay off or the feedback wire is shorted to battery voltage.
Common causes
Most likely first.
- Relay contact stuck closed
- Feedback wire shorted to B+
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Alternative-fuel system warning light
- Alternative-fuel mode unavailable
How to diagnose it
- Check freeze-frame and live relay-command and sense data to establish whether high feedback occurred while the relay was commanded off.
- Inspect the relay and sense-wire harness for a stuck relay, damaged insulation touching a power feed, corrosion, or loose terminals.
- With the relay commanded off under the manufacturer's procedure, check whether relay output is still present.
- Test the sense wire for an unintended short to battery voltage and inspect connector contact condition.
- If the relay and wiring behave correctly, verify the module's sense input and command using the manufacturer's circuit procedure.
Common fixes
- Repair a sense wire shorted to a power feed.
- Replace the AFCM power relay if its contacts remain closed when de-energised.
- Clean or repair corroded or loose feedback-circuit terminals.
- Repair a confirmed module feedback-input fault.
Can I keep driving?
The alternative-fuel system may be disabled because the AFCM cannot trust its relay feedback. Avoid relying on that system until repaired; if the vehicle behaves unexpectedly or lacks another usable fuel mode, stop driving.
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.