U0603

Code

Generic U — Network/User

Lost Communication With Fuel Pressure Sensor A

Brand: Generic

Type: U — Network/User

Views: UK: 24 EN: 42 RU: 19

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or shorted wiring between fuel pressure sensor/module and ECU
Faulty fuel pressure sensor or sensor module
Poor connector pin contact (corrosion, bent pins, pushed-out pins)
Faulty ECU/PCM or intermediary module (gateway)
Failed or degraded CAN/LIN bus (missing termination, short to power/ground)
Blown fuse or loss of sensor/module power or ground

Symptoms

Stored U0603 DTC and possible illumination of MIL (depends on manufacturer)
No fuel pressure data displayed on diagnostic scanner or intermittent/erratic readings
Hard start, rough idle, poor acceleration, or engine stalling if ECU cannot control fuel pressure
Reduced engine performance or limp-home mode
Other network modules reporting related communication faults

What to check

Read and record U0603 plus any additional network DTCs and freeze frame data with a capable scan tool
Verify whether fuel pressure sensor data is present on the scanner (live data) and note behavior
Inspect connectors and wiring at the fuel pressure sensor/module for corrosion, damage, or looseness
Check fuses and power/ground at the sensor/module (verify reference voltage present)
Scan other control modules for communication errors to determine if issue is isolated or network-wide
Perform a continuity/short-to-power/short-to-ground check on the sensor wiring harness

Signal parameters

Fuel pressure sensor module power: typically switched battery (B+) or fused 12 V — verify presence with key on
Reference voltage for analog sensors: commonly 5.0 V or 3.3 V (if analog type)
Sensor signal voltage (analog type): commonly ~0.5–4.5 V proportional to pressure (vehicle-specific)
CAN bus idle voltages: CAN_H ≈ 2.4–2.6 V, CAN_L ≈ 2.4–2.6 V (recessive state); dominant state: CAN_H ≈ 3.5 V and CAN_L ≈ 1.5 V
Expected communication: regular CAN frames containing fuel pressure data; scanner should show update rate consistent with vehicle (e.g., several times per second)

Diagnostic algorithm

Connect a diagnostic scanner and confirm U0603 plus any other network codes; save freeze frame and live data.
Determine whether the fuel pressure value is missing, static, or erratic in live data. Note timestamp and conditions.
Inspect the fuel pressure sensor/module connector and harness for damage, corrosion, or moisture; repair as needed.
With key on, verify sensor/module power and ground at the connector; check reference voltage (if analog) and measure signal line.
If the sensor uses CAN/LIN, check for proper bus voltage at the module connector; compare to another known-good module location.
Perform wiring continuity and short tests between the sensor/module and the ECU/gateway pins; repair any opens/shorts.
If wiring and power/ground are good but no communication, substitute a known-good sensor/module (if available) or temporarily connect a known-good module to confirm behavior.
If module replacement fixes the issue, clear codes and retest. If problem persists, investigate the gateway/ECU communication interface (inspect termination resistors and related modules).
Check for technical service bulletins (TSBs) or software updates for the ECU/gateway or sensor module; reflash/update as needed.
After repairs, clear codes and perform a full road test and rescans to confirm fault does not return.

Likely causes

Damaged/loose connector at fuel pressure sensor or module
Broken or shorted signal/power/ground wire in harness
Failed fuel pressure sensor/module
CAN bus fault between sensor module and gateway/ECU
ECU/gateway internal failure or software communication error

Fault status

⚠️ Status

Lost Communication With Fuel Pressure Sensor A — the vehicle network controller is not receiving valid data from the fuel pressure sensor or its module. Check wiring, connectors, power/ground, and CAN/LIN communication.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

Repair manuals