P2668: Fuel Mode Indicator Lamp Control Circuit

What it means

The fuel mode indicator lamp circuit (showing whether a bi-fuel vehicle currently runs on gasoline or alternative fuel) is faulty. Driver may not know the active fuel.

At a glance

• Usually lights the check-engine light

How it works

A bi-fuel vehicle's fuel-mode indicator circuit tells the instrument cluster which fuel mode is active, such as gasoline or an alternative fuel. This code sets when the module detects a fault in that indicator-lamp control circuit, so the display may be missing or misleading.

Common causes

Most likely first.

1. Burnt-out indicator bulb
2. Open or shorted wire to the cluster

Symptoms

• Check-engine light
• Fuel-mode indicator may be absent or incorrect

How to diagnose it

1. Record freeze-frame data and check live data, if available, to confirm the selected and active fuel modes while comparing them with the cluster display.
2. Inspect the fuel-mode indicator in the instrument cluster for a failed lamp or display segment.
3. Check the cluster and fuel-mode indicator connectors and wiring for a loose connection, open, short, or corrosion.
4. Test continuity and check for shorts in the indicator control circuit according to the manufacturer's wiring information.
5. If the lamp and wiring pass, test the cluster or control-module output using the manufacturer's diagnostic procedure.

Common fixes

• Replace a failed fuel-mode indicator bulb if the vehicle uses a replaceable bulb.
• Reconnect or clean a loose or corroded cluster or indicator connector.
• Repair an open or short in the fuel-mode indicator wiring.
• Repair the cluster or control-module fault if circuit testing confirms it.

Can I keep driving?

You can generally drive if the vehicle otherwise runs normally, but verify the active fuel mode using the vehicle's controls or other available indicators before driving. If you cannot tell which fuel is in use or the vehicle switches modes unexpectedly, avoid relying on it until checked.