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U0604 Lost Communication With Fuel Pressure Sensor B

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Sensor B is the second fuel pressure measuring point, for example a low-pressure sensor in the feed line of a direct injection engine or a second rail on V engines; which pressure it reads depends on the maker. U0604 flags that this digital sensor has stopped sending valid SENT frames to the engine controller. Nobody publishes a manufacturer description for this code. By analogy with Ford's SENT checks for oil and filter pressure sensors, the controller would look for driver errors, a line held high or low or missing frames and confirm after a few seconds. CARB 1968.2 requires separate lost-communication codes for coded digital inputs. P018A is the analog circuit code for sensor B, U0603 the counterpart for sensor A. Depending on the role, pump control or the second rail falls back to defaults.

Likely causes

Damaged signal, supply or ground wire to sensor B
Sensor B failed internally
Sensor A and B connectors swapped or loose

Symptoms

  • Check engine light on
  • Hesitation or reduced power under load

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–450
Time0.3–2 h

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

Parts involved

fuel pressure sensor bsensor wiring

Related codes

U0603P018A

References: en.wikipedia.org, law.cornell.edu.