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Home / DTC / U066F — Lost Communication With Low Pressure Fuel System Sensor

U066F — Lost Communication With Low Pressure Fuel System Sensor

Detailed page for trouble code U066F.

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Code

U066F

Generic U — Network/User

Lost Communication With Low Pressure Fuel System Sensor

Brand: Generic
Type: U — Network/User
Views: UK: 18 EN: 30 RU: 17
AI status
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Page language: EN

Causes

  • Open, shorted, or corroded wiring between sensor/module and main control module
  • Faulty or poorly seated connector at the sensor/module
  • No power (fuse, relay, wiring) or poor ground to the sensor/module
  • Failed low-pressure fuel system sensor or sensor module
  • CAN/LIN bus fault, missing termination, or network interference
  • Intermittent connection (broken wire inside harness) or water ingress

Symptoms

  • Malfunction Indicator Lamp (MIL) or network warning illuminated
  • No fuel pressure reading available in scan tool PIDs for low-pressure sensor
  • Intermittent or no engine start, rough idle, or reduced performance (if fuel control affected)
  • Possible limp-home mode if vehicle control strategy requires the sensor
  • Other communication-related DTCs present (network errors)

What to check

  • Read all stored and pending DTCs and note freeze frame/occurrence data
  • Check for other network communication DTCs (U0100, U0121, etc.)
  • Inspect sensor connector for corrosion, bent pins, moisture, or damage
  • Verify fuses and relays that feed the sensor/module
  • Backprobe or disconnect connector and measure reference voltage and ground
  • Check wiring continuity and resistance between sensor and the ECU/network node

Signal parameters

  • Analog-type pressure sensors: signal typically spans ~0.5–4.5 VDC proportional to pressure (verify OEM spec)
  • Sensor power supply commonly uses a regulated 5 V reference; measure key-on voltage at sensor connector
  • Digital sensor/module: periodic CAN/LIN messages for pressure data — update rate is vehicle-specific (typically 1–10 Hz or faster)
  • CAN bus idle/differential behaviour: messages present on bus when modules communicating; missing or no activity indicates bus or node problem
  • Ground resistance: sensor ground should be low (near 0 ohms to chassis); high resistance can cause communication/failure

Diagnostic algorithm

  1. Connect a capable scan tool. Record U066F and any related codes, freeze frame, and live PIDs for fuel pressure and network status.
  2. Verify whether the low-pressure fuel PID is present and updating. Note if other modules are reporting normally on the same bus.
  3. Visually inspect the sensor/module connector and harness for corrosion, water ingress, damage, or loose pins. Repair as needed.
  4. With key ON engine OFF, backprobe the sensor connector: confirm reference voltage (typically 5 V), signal voltage, and ground continuity to chassis. Compare to OEM specs.
  5. Check fuses and relays that supply the sensor/module. Replace faulty items and recheck communication.
  6. Verify wiring continuity between sensor and its control module/ECU. Look for opens, shorts to battery or ground, and intermittent faults (wiggle test while monitoring).
  7. Check network physical layer: measure CAN/LIN voltages and observe message traffic with a scope or CAN bus analyzer. Confirm termination resistors and absence of excessive noise.
  8. If wiring and bus tests are good, substitute a known-good sensor or module (if available) and recheck communication.
  9. Clear codes and perform a road/drive cycle or reproduce conditions to confirm whether U066F returns.
  10. If the fault persists after sensor/module substitution and wiring is verified, consider module replacement or dealer-level diagnostics for control module software/firmware updates.

Likely causes

  • Damaged connector pins or corrosion at the low-pressure fuel sensor
  • Open or short in sensor signal or CAN/LIN communication wires
  • Blown fuse or failed power supply to the sensor/module
  • Failed low-pressure fuel sensor/module
  • CAN bus termination resistor missing or short to battery/chassis
  • Intermittent harness damage (chafing, pinch) causing dropouts

Fault status

⚠️ Status
U066F — Lost Communication With Low Pressure Fuel System Sensor: the vehicle controller did not receive expected messages or valid data from the low-pressure fuel sensor/module. The fault may be intermittent or permanent; further electrical and network diagnostics are required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

Similar codes

U0100 U0121 U0122 U0140 U0299 P0191
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