Network, generic

U0691 Lost Communication With Exhaust Pressure Sensor A

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

On Ford's 6.7 L and 3.0 L diesels of 2023, exhaust pressure sensor A measures pressure ahead of the turbine and is a SENT device. Ford's diesel OBD summary sets U0691 when the low-level SENT driver sees a communication error or no data within the expected window, when the line is held at one voltage level, or when the sensor reports an internal fault; the check runs continuously and needs 5 s. P0470 is kept for a SENT status error or a raw value above a limit. The same sensor has two plausibility tests: with the engine off it may differ from barometric pressure by no more than 15 kPa (P0471), and while driving it is compared against a model (P0474). Without this pressure, turbo and EGR control lose an input. U0692 covers sensor B.

Likely causes

SENT line shorted to ground or supply, or open, near the hot turbo

Sensor reports an internal error or stops sending

Connector heat-damaged or corroded

Sensor damaged by soot or condensate in the pressure line

Symptoms

Check engine light
Reduced boost or power on some engines
EGR and turbo running on substitute values

Repair estimate

DifficultyMediumDIY possible

Parts and labour€60–400

Time0.5–2 h

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

Parts involved

exhaust pressure sensor avehicle bus wiring

References: fordservicecontent.com, law.cornell.edu.