P2A35: AFCM Power Relay Sense Circuit

What it means

The AFCM detects a generic fault on the sense feedback line of its power relay. Relay state cannot be confirmed reliably.

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 supply to the alternative-fuel control module, and a separate sense line reports the relay's output state. The module sets P2A35 when that feedback is unreliable, so it cannot confirm whether the relay contacts actually switched as commanded.

Common causes

Most likely first.

1. Open or shorted feedback wire
2. Relay contact aged - high resistance

Symptoms

• Check-engine light
• Alternative-fuel system warning light
• Alternative-fuel mode unavailable

How to diagnose it

1. Review freeze-frame data and AFCM relay command and sense status to identify whether feedback failed during switching or remained implausible.
2. Inspect the relay, socket, sense-wire harness, and connectors for looseness, corrosion, damaged insulation, or backed-out pins.
3. Check sense-wire continuity and isolation from ground and power as appropriate under the manufacturer's circuit procedure.
4. Inspect relay contacts and socket for heat damage or poor contact, then check relay output while it is commanded on.
5. If the circuit and relay are sound, compare module command and feedback readings using the manufacturer's diagnostic procedure.

Common fixes

• Reseat the relay and repair loose or corroded sense-line terminals.
• Repair an open or shorted relay feedback wire.
• Replace the AFCM power relay if its contacts have excessive resistance or fail to switch reliably.
• Repair a confirmed module connector or feedback-input fault.

Can I keep driving?

Alternative-fuel mode may be unavailable because the AFCM cannot confirm its power relay state. Use another available fuel mode only if the vehicle operates normally, and avoid relying on the alternative-fuel system until repaired.