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U066F Lost Communication With Low Pressure Fuel System Sensor

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

The low-pressure side of a direct-injection fuel system runs from the tank pump to the high-pressure pump, and a sensor there lets the controller regulate the lift pump. If that sensor transmits a digital value, for example over SENT, U066F records that its messages have stopped. None of the public manufacturer documents uses the code. GM's 2025 table 25OBDG03A reads its low-side sensor, labelled fuel pressure sensor B, as a 5 V analog input at the engine controller or the pump module and fails P018C below 4 % of reference (64 failed samples in 80, Type B). Ford's 2024 summary flags its low-pressure rail sensor below 0.049 V or above 4.88 V within 8 s. Analog faults of this sensor are P2539 to P2543. Expect a MIL and possibly hard starting or hesitation under load.

Likely causes

Signal, supply or ground wire to the low-pressure sensor damaged

Connector at the sensor or fuel line corroded or not latched

Sensor electronics failed and no longer transmit

Receiving input or software of the engine or pump control module faulty

Symptoms

Check engine light
Longer cranking or hard starting
Hesitation or power loss under heavy load

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€60–450

Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

low pressure fuel sensorvehicle bus wiring

References: law.cornell.edu, gsi.ext.gm.com, fordservicecontent.com.