U0665: Lost Communication With Fuel Rail Pressure Sensor Bank 2

What it means

The vehicle bus reports loss of communication with smart fuel rail pressure sensor on bank 2. The high-pressure fuel control loop loses its actual feedback; injection switches to a fail-safe map.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The bank 2 fuel rail pressure sensor sends pressure information over the vehicle network so the engine controller can regulate high-pressure fuel delivery. U0665 sets when messages from this specific sensor are lost, leaving the controller without normal bank 2 pressure feedback and potentially causing fail-safe operation.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan the engine and network modules, save freeze-frame data, and note any fuel-pressure or communication codes that can show whether the fault is isolated to bank 2.
2. Compare bank 2 rail-pressure data and sensor communication status with bank 1, if available, and note any reduced-power or fail-safe indications.
3. With the engine off and following safety precautions for high-pressure fuel, inspect the bank 2 sensor connector and harness for damage, contamination, loose terminals, or chafing.
4. Check the sensor's specified power and ground and inspect shared fuses or feeds identified in the wiring diagram.
5. Test the network circuit to the bank 2 sensor for opens, shorts, and abnormal resistance according to the manufacturer procedure.
6. If power, ground, and bus wiring pass, use the manufacturer's sensor communication and fuel-pressure diagnostic procedure before replacing the bank 2 sensor.

Common fixes

• Secure the bank 2 fuel rail pressure sensor connector and clear contamination if appropriate.
• Repair damaged or corroded wiring at the bank 2 sensor.
• Restore a failed power or ground feed to the sensor.
• Repair an open or short in the network circuit serving the bank 2 sensor.
• Replace the bank 2 fuel rail pressure sensor only after its circuit and communication checks pass.

Can I keep driving?

Avoid driving if the engine runs roughly, loses power, stalls, or shows a fuel-system warning; loss of bank 2 pressure feedback can affect fueling and emissions. If it runs normally, limit driving to a short trip for diagnosis and avoid heavy loads or hard acceleration.