U0105 – Lost Communication With Fuel Injector Control Module

System: Network | Standard: ISO/SAE Controlled | Fault type: General

Definition source: SAE J2012/J2012DA (industry standard)

DTC U0105 indicates the vehicle has detected a loss of communication with the Fuel Injector Control Module over the network. This is a network communication fault, not a direct statement that injectors, fuel quality, or engine mechanical components have failed. When U0105 sets, other modules are no longer receiving expected messages from the Fuel Injector Control Module (or are unable to exchange data with it), which can lead to drivability changes or even a no-start depending on how the platform is designed. DTC behavior, symptom severity, and the exact module location and wiring layout vary by vehicle, so confirm the affected network, power/ground routing, and diagnostic procedures using the applicable service information.

What Does U0105 Mean?

U0105 – Lost Communication With Fuel Injector Control Module means the vehicle’s networked control modules have detected that communication with the Fuel Injector Control Module has been lost. Per SAE J2012 DTC conventions, this “U” code is in the network communication family, and the definition is strictly about missing or invalid data exchange between modules, not a direct injector circuit electrical fault. In practice, one or more modules stop receiving required, periodic messages from the Fuel Injector Control Module (or cannot complete network handshakes), and a communication timeout or invalid-message condition causes U0105 to be stored.

Quick Reference

• Subsystem: Network communication path to/from the Fuel Injector Control Module (data bus, module power/ground, and related connectors).
• Common triggers: Module offline, network bus open/short, high resistance at connectors, weak power/ground to the module, or intermittent connection during vibration.
• Likely root-cause buckets: Wiring/connector faults; power/ground feed issues; network bus faults; module internal failure; configuration/software issues (varies by vehicle).
• Severity: Medium to high; may cause reduced power, rough running, stalling, or a no-start depending on how fueling is managed.
• First checks: Scan for companion U-codes, confirm which modules can communicate, check module power/ground integrity, and inspect network wiring/connectors near the module.
• Common mistakes: Replacing injectors or fuel system parts before verifying network communication, power/ground, and connector condition.

Theory of Operation

The Fuel Injector Control Module (where used) exchanges operating data with other controllers over the vehicle network. This may include injector commands, enable states, diagnostics, and status messages. Other modules expect these messages at regular intervals; if the data is missing, corrupted, or the module stops responding, they may set a lost-communication DTC. The module also typically requires stable battery feed(s), ignition feed(s), and solid ground connections to remain online.

U0105 is set when a controller detects a communication timeout or cannot validate the expected network traffic associated with the Fuel Injector Control Module. The underlying reason is often not the data itself but the conditions that prevent communication, such as loss of module power, poor ground, network wiring faults, or connector problems that become intermittent with heat, vibration, or movement.

Symptoms

• No-start: Engine may crank but not start if injector control is disabled or unavailable.
• Stalling: Engine may stall unexpectedly if communication drops out while running.
• Reduced power: Limited throttle response or limp mode behavior may occur to protect the system.
• Rough running: Misfire-like behavior or unstable idle may be present due to disrupted fueling control.
• Warning lamp: Malfunction indicator or system warning indicators may illuminate alongside stored U-codes.
• Intermittent concern: Symptoms may come and go with bumps, harness movement, or temperature changes.

Common Causes

• Open, shorted, or high-resistance wiring in the network communication circuits between the Fuel Injector Control Module and other modules
• Poor connector engagement, backed-out terminals, corrosion, moisture intrusion, or terminal spread at the Fuel Injector Control Module or network junctions
• Loss of power supply feed(s) to the Fuel Injector Control Module (blown fuse, faulty relay, open in feed circuit)
• Loss of ground path(s) to the Fuel Injector Control Module (loose ground fastener, corroded ground point, damaged ground wire)
• Network bus fault affecting multiple modules (short between network lines, short to power/ground, damaged splice/junction)
• Fuel Injector Control Module internal fault that prevents communication (hardware failure)
• Module software/firmware issue causing the Fuel Injector Control Module to stop responding on the network (varies by vehicle)
• Aftermarket electrical accessories or recent electrical work introducing wiring damage, poor splices, or incorrect pinning near the network circuits

Diagnosis Steps

Tools typically needed include a scan tool capable of full-network scans and retrieving freeze-frame/network status data, a digital multimeter, and service information with wiring diagrams, connector views, splice/ground locations, and test procedures. A back-probing kit and terminal inspection tools help verify pin fit and terminal condition. A battery charger/maintainer is recommended to keep system voltage stable during testing.

1. Confirm the complaint and run a full vehicle network scan. Record all codes (current, pending, history) from every module and save freeze-frame data. Note whether U0105 is current or history and whether multiple “lost communication” codes are present.
2. Check scan tool communication with the Fuel Injector Control Module directly (if the scan tool allows module selection). If the module is not reachable, treat this as an active communication/power/ground/network integrity problem until proven otherwise.
3. Review code setting context using service information (varies by vehicle). Note any prerequisites such as ignition state, crank/run state, or network sleep/wake conditions that can influence when the monitor runs.
4. Perform a quick visual inspection before electrical testing: harness routing near hot components, sharp edges, recent repairs, and areas where the harness flexes. Inspect the Fuel Injector Control Module connector(s) for incomplete seating, broken locks, bent pins, corrosion, or water traces.
5. Check the simplest electrical causes first: verify all related fuses and relays that supply the Fuel Injector Control Module. If a fuse is open, do not replace it repeatedly without checking the circuit for shorts and harness damage.
6. Verify Fuel Injector Control Module power and ground integrity under load. Use voltage-drop testing on the module’s power feed(s) and ground path(s) while the circuit is powered (key on, and follow service info for when the module should be awake). Excessive drop indicates resistance in wiring, connections, relays, grounds, or splices that can cause communication loss.
7. Inspect and test network wiring integrity between the Fuel Injector Control Module and the network backbone. With the system powered down per service info, check for obvious opens/shorts in the network circuits and confirm connector terminal tension and pin fit. Repair any damaged twisted pair sections using approved practices for the platform.
8. Wiggle test: with the scan tool monitoring network/module status and U0105 status, gently manipulate the harness and connectors at the Fuel Injector Control Module, network splices, and pass-through points. If communication drops in/out or related parameters glitch, isolate the exact location and inspect terminals, splices, and wire strands closely.
9. If multiple modules show communication faults, broaden the scope: inspect shared network junctions/splices and shared power/ground points. A single compromised splice or ground can create widespread network symptoms that appear as multiple “lost communication” codes.
10. Log live data during the failure. If the scan tool provides network health indicators or module online/offline status, record a short log while recreating the condition (key cycles, vibration, temperature change if applicable). Use the timestamped data to correlate the dropout with a specific circuit disturbance or operating event.
11. Only after power, ground, connector condition, and network wiring are verified should the Fuel Injector Control Module itself be considered suspect. Follow service information for any directed tests, module reset procedures, and required setup/programming steps if module replacement is authorized.

Professional tip: Treat U0105 as a “prove the basics” fault: a module that can’t communicate often cannot report its own internal issues. Prioritize confirming stable power and ground with voltage-drop tests, then isolate the network fault with connector/terminal inspection and a controlled wiggle test while monitoring module online status. Avoid condemning a module until wiring, connectors, and shared network points are verified.

Possible Fixes & Repair Costs

Repair cost for U0105 varies widely because the fault can be caused by anything from a simple connector issue to a network or module power/ground problem. Accurate diagnosis first will determine whether the fix is wiring, power supply, network integrity, or the module itself.

• Clean, reseat, and secure Fuel Injector Control Module connectors; correct poor pin fit, backed-out terminals, or corrosion found during inspection
• Repair or replace damaged wiring in the communication network circuits to the Fuel Injector Control Module (chafing, open circuits, shorts between network lines, or shorts to power/ground)
• Restore correct module power and ground feeds by repairing blown fuses, faulty relays, loose grounds, or high-resistance connections verified by testing
• Repair shared network issues by addressing faults at splices, junctions, or other modules that are disrupting network communication
• Update, configure, or perform required setup procedures for the Fuel Injector Control Module when service information indicates a software or configuration-related communication fault
• Replace the Fuel Injector Control Module only after confirming proper power/ground and a healthy network with the fault still present

Can I Still Drive With U0105?

Driving with U0105 is not recommended if the vehicle has a no-start, stalling, reduced power, or unstable idle condition, because lost communication with the Fuel Injector Control Module can affect fuel delivery control and may become intermittent without warning. If the vehicle appears to drive normally, you may be able to drive a short distance to a repair location, but monitor for sudden drivability changes and avoid high-demand situations. If warning lights related to powertrain control appear or the engine runs poorly, stop driving and diagnose the communication, power/ground, and network circuits first.

What Happens If You Ignore U0105?

Ignoring U0105 can lead to intermittent or worsening drivability issues as the communication loss becomes more frequent, including hard starts, stalls, reduced power, or a no-start. Continued operation with an unresolved network or power/ground fault can also create additional communication codes, complicate diagnosis, and increase the chance of an unexpected breakdown.

Last updated: March 14, 2026

Vehicles Commonly Affected by U0105

• Vehicles that use a dedicated Fuel Injector Control Module rather than controlling injectors only through a single engine controller
• Platforms with multiple control modules sharing a common communication network for powertrain functions
• Vehicles exposed to harsh vibration environments that can stress harness routing and connector retention
• High-mileage vehicles where connector terminal tension and ground connections may degrade over time
• Vehicles that have had recent engine, fuel system, or wiring repairs where connectors or harnesses may not be fully seated
• Vehicles with known susceptibility to corrosion at under-hood connectors, fuse/relay centers, or ground points
• Applications where the Fuel Injector Control Module is mounted away from the engine controller and relies heavily on network integrity
• Vehicles with prior electrical modifications that may affect shared power, grounds, or network routing