P2687: Fuel Supply Heater Control Circuit / Open

What it means

The controller cannot drive the diesel fuel filter or supply line heater. In cold weather diesel waxing can clog the filter.

At a glance

• Usually lights the check-engine light

How it works

The fuel supply heater warms diesel around the filter or supply line to help prevent wax from restricting flow in cold conditions. The control module checks whether it can operate the heater through its control circuit. P2687 sets when that circuit is open, so the module cannot drive the heater as expected.

Common causes

Most likely first.

1. Open heater element
2. Failed heater relay

Symptoms

• Check-engine light
• Hard starting in cold weather
• Poor running in cold weather

How to diagnose it

1. Read freeze-frame data and note the ambient and coolant temperatures, since a cold-weather starting complaint helps confirm when the heater matters.
2. Inspect the fuel heater connector and nearby wiring for disconnection, damage, or corrosion that could leave the circuit open.
3. With the circuit safely isolated as specified by the manufacturer, check the heater element for continuity and compare the result with the manufacturer's specification.
4. Check the heater relay and its socket for an open coil, poor seating, or damaged terminals.
5. Trace the heater control circuit between the module, relay, and heater for a break, then clear the code and see whether it returns.

Common fixes

• Reconnect or clean a loose or corroded fuel heater connector.
• Repair an open or damaged section of heater wiring.
• Replace a failed fuel supply heater element.
• Replace a relay that fails the manufacturer's electrical checks.

Can I keep driving?

If the engine runs normally in mild weather, a short trip may be possible, but avoid relying on the vehicle in cold conditions. Without the heater, diesel can wax and restrict the filter, leading to hard starting, poor running, or a stall.