U0105

Universal

Lost Communication With Fuel Injector 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
High Severity

The vehicle has detected that other control modules are not receiving expected messages from the fuel injector control module (FICM). The FICM manages injector operation in vehicles equipped with this system. A communication fault can affect starting, engine operation, or power, but the code does not by itself prove that the FICM has failed. Exact system design and procedures depend on the vehicle.

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⚠️ Before You Begin (Safety First)

If the engine stalls, will not restart, or runs so poorly that the vehicle cannot be controlled safely, pull over when safe and arrange assistance rather than continuing to drive. If there are no symptoms, drive cautiously and have the fault diagnosed soon; communication problems can be intermittent.

Common Symptoms

  • The engine may crank but fail to start if injector control is disrupted.
  • The engine may stall or run roughly if communication is lost while it is operating.
  • Reduced power or an engine warning light may occur, depending on how the vehicle responds to the communication fault.
  • Other communication-related warning lights or codes may appear because multiple modules share network messages.
  • There may be no noticeable symptoms if the fault is intermittent or the vehicle's control strategy maintains normal operation.

Common Causes

  • An intermittent or open connection in the FICM's wiring or network connections can interrupt messages.
  • Corrosion, looseness, or damage at a relevant connector can interfere with communication.
  • A power supply or ground problem can prevent the FICM from operating or communicating reliably.
  • Low or unstable vehicle voltage can disrupt module operation or network communication.
  • A fault elsewhere on the shared communication network can affect messages to or from the FICM.
  • The FICM itself may have an internal fault, but testing is needed before concluding that it needs replacement.

Diagnostic Steps

  1. Note whether the engine has starting, stalling, rough-running, or warning-light symptoms; this helps establish how urgently the fault needs attention.
  2. With the vehicle safely parked, check the battery condition and look for loose or visibly damaged battery connections, since unstable voltage can affect module communication.
  3. With the ignition off, visually inspect accessible FICM-related connectors and wiring for looseness, corrosion, or damage. Do not force connectors or probe terminals without the correct service information.
  4. Check only the relevant fuses identified in the vehicle's owner or service information. Replace a blown fuse only with the specified type and rating; if it blows again, stop and seek diagnosis.
  5. If a suitable scan tool is available, record U0105 and any related codes from all modules before clearing anything. A scan of other modules can help distinguish a FICM issue from a wider network or power problem.
  6. If the fault returns or requires electrical network testing, have a qualified technician follow vehicle-specific diagnostic procedures rather than replacing the FICM based on the code alone.

When to Call a Professional

Use a scan tool capable of communicating with all vehicle modules. Check whether U0105 is current or intermittent and look for related communication, power, or ground codes. Confirm the FICM's power and grounds and inspect network wiring and connectors using the vehicle-specific service information before considering module replacement. Follow the correct setup or programming procedure if a module is replaced.

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Commonly Asked Questions

Does U0105 prove that the fuel injector control module has failed?

No. It indicates lost communication with the module. Wiring, connectors, power, grounds, voltage, or another network problem can cause the same detected condition.

Can a vehicle have U0105 without noticeable symptoms?

Yes. An intermittent communication fault or the vehicle's response strategy may leave normal operation apparently unchanged, though the fault still warrants diagnosis.

Why should other modules be scanned too?

Related codes across several modules can help show whether the issue is limited to communication with the FICM or involves a broader network, power, or ground problem.

Is it safe to keep driving with U0105?

It depends on the symptoms. If the engine stalls, will not restart, or runs too poorly for safe control, stop driving when safe and arrange assistance. With no symptoms, use caution and arrange diagnosis soon.

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