P2A34: AFCM Power Relay Control Circuit High

What it means

Voltage on the AFCM power relay control line is above the expected window. Wire shorted to B+ or coil open.

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 provides switched power to the alternative-fuel control module. The engine control module monitors the relay control-line voltage and sets P2A34 when it is higher than expected, which can happen if the wire is shorted to battery voltage or the relay coil is open.

Common causes

Most likely first.

1. Control wire shorted to B+
2. Open relay coil
3. Connector pins corroded - high contact resistance

Symptoms

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

How to diagnose it

1. Record freeze-frame data and relay-command status to determine whether the high reading appeared with the relay on or off.
2. Inspect the relay and its control-wire routing for contact with battery feeds, damaged insulation, corrosion, or loose connector terminals.
3. Check the AFCM power relay coil for an open circuit using the manufacturer's procedure and specification.
4. With the relay disconnected as directed, test the control wire for an unintended connection to battery voltage.
5. If the relay and wire test normally, verify connector contact and module command using the manufacturer's circuit procedure.

Common fixes

• Repair a control wire shorted to a battery-voltage feed.
• Replace the AFCM power relay if its coil is open.
• Clean or repair corroded or loose relay connector terminals.
• Repair a confirmed module connector or control-output fault.

Can I keep driving?

The alternative-fuel system may be disabled, while another available fuel mode may remain usable. Do not rely on alternative-fuel operation until repaired, and stop if the vehicle cannot run safely on an available fuel.