P027D: Fuel Pump Module B Control Circuit High

What does P027D mean?

On demand-controlled fuel systems the engine module does not drive the pump itself but sends a pump control module the desired pump output on a separate control line, usually as a duty cycle; the module reports back on a monitor line or via CAN. Module B is a second pump module, for example on dual-tank commercial vehicles. P027D means the control circuit to pump module B reads high, typically a short to voltage – the counterpart of P025D. Ford lists it in the low-pressure lift pump monitor of its 2023 diesels, monitored continuously and set within 0.5 s, without its own threshold. Pump B may then run all the time or not at all.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Pump B runs all the time or not at all
• Starting problems

Common causes

• High Control line to module B shorted to voltage
• Medium Moisture or corrosion in the connector
• Medium Pump control module B faulty

Likelihood is a general estimate across vehicles; your make and model may differ.