U0119

Universal

Lost Communication With Fuel Cell Control Module

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The vehicle has detected that other control modules are not receiving expected messages from the fuel cell control module. That module helps manage fuel cell operation, but the code alone does not prove that the module itself has failed. Depending on the vehicle and whether the fault is current, the result may be a warning, reduced power, or a no-start; an intermittent or stored code may cause no noticeable symptoms.

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⚠️ Before You Begin (Safety First)

If the vehicle loses power, will not operate normally, or displays a stop or powertrain warning, pull over somewhere safe and arrange assistance rather than continuing to drive. Do not open or work on high-voltage or fuel-cell components, or hydrogen-system parts; have those inspected by a qualified technician.

Common Symptoms

  • A warning light or message may appear if the communication loss affects vehicle operation or monitoring.
  • Reduced power or limited fuel-cell operation may occur if the vehicle cannot receive information needed to manage the system.
  • The vehicle may fail to start or may stop operating if communication loss prevents required control functions.
  • There may be no noticeable symptoms if the code is intermittent, stored, or does not affect operation at that time.

Common Causes

  • A loose, damaged, corroded, or poorly connected wiring or connector in the module's power, ground, or communication circuits can interrupt messages.
  • Low or unstable vehicle electrical-system voltage can disrupt module operation or network communication.
  • A fault elsewhere on the vehicle communication network may prevent messages from reaching or leaving the fuel cell control module.
  • The fuel cell control module may have an internal fault, but the code alone does not establish that diagnosis.
  • A software or configuration issue may interfere with communication; applicability and checks depend on the vehicle.

Diagnostic Steps

  1. Note any warning messages and whether the vehicle has reduced power, will not start, or has other unusual behavior; this helps determine urgency and gives a technician useful context.
  2. With the vehicle safely parked and switched off as directed by its owner's manual, look for obvious damage or looseness in accessible low-voltage battery connections. Do not disconnect components unless the vehicle-specific instructions say it is safe.
  3. Visually check only readily accessible, non-high-voltage wiring and connectors for damage or disconnection. Do not remove covers or handle wiring identified as high voltage, fuel-cell, or hydrogen-system equipment.
  4. If a suitable scan tool is available, record all codes and note which modules communicate; avoid clearing codes before the information has been recorded.
  5. If the code returns or the vehicle has operational symptoms, arrange diagnosis using service information for the exact model, year, and engine or powertrain.

When to Call a Professional

A technician should check for related communication and power-supply codes, confirm whether the fuel cell control module is supported and communicating on this vehicle, and inspect its power, ground, connectors, and network wiring using vehicle-specific service information. A module should not be replaced until wiring, supply voltage, grounds, and network faults have been evaluated.

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Commonly Asked Questions

Does U0119 prove that the fuel cell control module needs replacement?

No. It reports lost communication, which can result from power, ground, wiring, connector, network, or module problems. Diagnosis should distinguish among these before parts are replaced.

Can the vehicle still drive with this code?

Possibly, but behavior depends on the vehicle and whether the communication loss is active. Reduced power, a no-start, or other operating limits may occur. Follow any vehicle warnings and stop safely if operation becomes abnormal.

Why might there be no warning or noticeable symptom?

The fault may be intermittent or stored, or communication loss may not affect a function the driver notices at that moment. A scan can help establish whether the code is current and what other modules reported.

What should be checked before suspecting the module?

A technician should review related codes and verify the module's power and ground, connector condition, and communication-network integrity using vehicle-specific procedures.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.