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DTC codes / U35xx · Network communication / U3565

U3565Hydrogen Supply Line A Pressure Sensor 2 Circuit

U3565 is a manufacturer-specific network code indicating that the powertrain control module has lost valid data from the Hydrogen Supply Line A Pressure Sensor 2 circuit, which is used on hydrogen fuel cell and hydrogen internal combustion vehicles to monitor pressure in the supply line. The computer detected an out-of-range signal, a circuit fault, or a missing message from that sensor over the communication bus, so it cannot trust the pressure reading for fuel delivery or safety calculations.

SystemNetwork
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaNetwork communication

Symptoms you may notice

  • Illumination of the malfunction indicator lamp, often with no other noticeable symptoms besides the warning light
  • Reduced power or a limp-home mode because the controller cannot verify hydrogen supply pressure
  • Rough running, hesitation, or misfire under load if the pressure signal is erratic
  • A message on the driver information display warning of a hydrogen system fault or service required
  • Inability to start or a shutdown immediately after start if the controller treats the missing pressure signal as unsafe
  • Other communication or sensor codes stored alongside U3565 in modules on the same network

Common causes, most likely first

  1. A failed or contaminated Hydrogen Supply Line A Pressure Sensor 2, which is exposed to hydrogen and can drift or fail internally
  2. Damaged, chafed, or corroded wiring or connector pins in the sensor circuit, especially near high-pressure fittings and heat sources
  3. A poor ground or reference voltage supply shared with the sensor, causing the signal to fall out of range
  4. A controller or module that has lost communication on the bus, so the pressure message never arrives at the module that sets U3565
  5. Low or unstable hydrogen supply pressure that pushes the sensor signal outside its expected range
  6. Water or debris intrusion into the sensor connector or harness, common in vehicles that sit or operate in wet conditions
  7. A software or calibration issue in the module that interprets the pressure sensor message, requiring a reflash or update

How to diagnose and fix it

  1. Connect a scan tool and record all stored codes, freeze-frame data, and live pressure sensor values before clearing anything
  2. Inspect the Hydrogen Supply Line A Pressure Sensor 2 connector and harness for corrosion, chafing, and loose pins, and repair as needed
  3. Check the sensor reference voltage and ground at the connector with a multimeter, comparing against the manufacturer's specification
  4. Verify actual hydrogen supply pressure with a mechanical gauge or the vehicle's own service port, and compare it with the sensor reading
  5. Perform a wiggle test on the harness while watching live data to catch intermittent circuit faults
  6. Replace the pressure sensor only after electrical and pressure checks confirm it is the faulty part, then clear codes and verify the repair
  7. If the circuit and sensor test good, check for communication faults on the network and update or replace the affected module as directed by service information

What the pressure sensor code hides

  • U3565 is often set by a communication dropout rather than a failed sensor, so technicians who replace the sensor first frequently find the code returns because the real fault is a chafed wire or a module losing power.
  • Hydrogen pressure sensors are exposed to a demanding environment, and a sensor that reads correctly at idle can still drop out under vibration or temperature swings, so live data must be watched during a road test.
  • A low hydrogen supply pressure from a failing regulator or a nearly empty tank can push the sensor signal out of range and set this code, which means the sensor itself may be reporting the truth.
  • Because this is a generic SAE J2012 code, the exact circuit layout and the module that sets it vary by manufacturer, so the service information for the specific vehicle is essential before probing pins.
  • Other codes on the same communication bus, such as U-codes for lost communication with the fuel cell control module, can accompany U3565 and point to a network problem rather than a sensor problem.

Can I keep driving with U3565?

Do not continue driving with U3565 on a hydrogen vehicle, because the controller cannot verify supply line pressure and may shut down the fuel system or enter a limp mode without warning. Have the vehicle inspected by a qualified technician before driving further, and avoid towing or high-load operation until the fault is repaired.

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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