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DTC codes / U06xx · Network communication / U0665

U0665Lost Communication With Fuel Rail Pressure Sensor Bank 2

U0665 is a communication fault that sets when the engine control module (ECM) stops receiving valid data from the bank 2 fuel rail pressure sensor over the vehicle's controller area network (CAN) bus. The ECM has detected a loss of the periodic message that carries fuel rail pressure readings for the bank 2 fuel rail, not necessarily a failure of the sensor itself.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaNetwork communication

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message, often with no other symptoms
  • Reduced engine power or limp-home mode triggered by the ECM when rail pressure data is missing
  • Rough running, misfire, or hesitation under load because the ECM cannot correctly meter fuel for bank 2
  • Hard starting or stalling, particularly on engines that rely on bank 2 rail pressure for startup fueling
  • A stored U0665 code accompanied by other communication or fuel system codes in the same module

Common causes, most likely first

  1. Damaged, chafed, or corroded wiring in the bank 2 fuel rail pressure sensor circuit or its CAN bus branch
  2. Loose or contaminated connector pins at the sensor, the ECM, or an intermediate harness splice
  3. Failed bank 2 fuel rail pressure sensor that no longer transmits data on the bus
  4. CAN bus communication fault such as a shorted or open data line affecting the sensor's message
  5. Low battery voltage or poor grounds causing intermittent module communication dropouts
  6. Software or calibration issue in the ECM that incorrectly flags the sensor message as missing
  7. Aftermarket electrical accessories or poor previous repairs introducing noise or resistance into the circuit

How to diagnose and fix it

  1. Perform a full scan of all modules and record every stored, pending, and permanent code before clearing anything
  2. Inspect the bank 2 fuel rail pressure sensor connector and harness for corrosion, pushed pins, or chafed insulation
  3. Check battery voltage, ground straps, and charging system output to rule out low-voltage communication faults
  4. Measure resistance and continuity on the sensor signal and CAN bus wires between the sensor and the ECM
  5. Verify the sensor's live data PID on a scan tool while wiggling the harness to catch intermittent dropouts
  6. If wiring and power are good, substitute a known-good bank 2 fuel rail pressure sensor and recheck communication
  7. Clear codes, perform a road test, and confirm the U0665 does not return before releasing the vehicle

Why U0665 is rarely a bad sensor

  • Most U0665 faults trace back to harness damage or connector corrosion rather than the bank 2 fuel rail pressure sensor itself, so resistance and wiggle tests come before parts replacement.
  • A weak battery or failing ground can set U0665 intermittently because the sensor's CAN message drops out when supply voltage sags during cranking.
  • The ECM may log U0665 alongside fuel trim or misfire codes for bank 2, and replacing the sensor without fixing the wiring will leave those codes unresolved.
  • Some vehicles route the bank 2 rail pressure sensor signal through an intermediate connector or splice that corrodes silently and is missed during a quick visual inspection.
  • Clearing U0665 without checking freeze-frame data can hide whether the fault occurred at key-on, idle, or under load, which changes where you start testing.

Can I keep driving with U0665?

You can usually drive to a repair shop if the engine runs normally and only the warning light is on, but avoid heavy throttle or towing because the ECM may be limiting fuel delivery on bank 2. If the engine is in limp mode, misfiring, or stalling, stop driving and have the vehicle towed to prevent damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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