U0105 — Data bus: injector control module – no communication

Failure code U0105 indicates that the vehicle’s ECU (Engine Control Unit) has lost communication with the injector control module via the data bus. This data bus is a network that allows different electronic control modules (ECMs) to exchange information. When communication is lost, certain engine functions may be impaired, which can affect vehicle performance.

Note: Labels for this fault code may vary between manufacturers. Some OEMs may assign different codes or descriptions but generally relate to communication issues with the injector control module.

Fast Facts

System affected: Engine Control Module network communication
Severity: Moderate to high, depending on the vehicle and symptoms
Main symptoms: Limp mode, poor acceleration, engine warning light
Driveability: Limited — driving is possible but not recommended until repaired

Manufacturer variations for trouble code U0105

Different vehicle manufacturers may use distinct labels or code variations for the same underlying issue related to loss of communication with the injector control module. Here are some known variations:

Audi / VW: U0105 – Data Bus: Injector Control Module – No Communication
BMW: U0105 – CAN Bus: Injector Control Module – No Communication
Ford: U0105 – Lost Communication with Injector Control Module
Mercedes-Benz: U0105 – Data Bus: Injector Control Module – No Communication
Renault: U0105 – Communication Bus with Injector Control Module – No Signal

What does trouble code U0105 mean?

U0105 points to a communication failure between the Engine Control Module (ECU) and the injector control module. The ECU continuously monitors the communication lines (commonly the CAN bus) to receive real-time data from various modules, including those controlling fuel injectors.

This code typically triggers when the ECU detects that it is not receiving expected signals or acknowledgments from the injector control module within a specified time frame. Such communication can be disrupted due to various reasons, leading to this diagnostic trouble code (DTC).

Usually, this code appears in specific driving or diagnostic contexts—such as after updating software, performing repairs, or if an electrical fault develops.

Severity and risks of trouble code U0105

The **severity** of U0105 hinges on the impact on engine operation. In some cases, the vehicle may operate normally, especially if other modules compensate, but in many instances, engine performance degrades, or the vehicle enters a limp mode to protect components.

**Potential risks** include increased emissions, poor fuel economy, unwanted rough running, or even engine stalling if communication is severely compromised. Additionally, ongoing communication issues can lead to further electrical system faults and complicate repairs.

**Can the vehicle be driven?** Limited — it is generally possible but not advisable to continue driving for extended periods until the underlying cause is diagnosed and repaired.

Symptoms of trouble code U0105

The presence of U0105 may cause various symptoms, though some vehicles may exhibit minimal signs. Common symptoms include:

Engine warning light illuminated on the dashboard
Reduced engine power or limp mode activation
Difficulty starting the engine or longer cranking times
Erratic idling or engine stalling
Poor acceleration or hesitation during driving
Transmission shifts may be affected due to communication issues

Most likely causes of trouble code U0105

Understanding the roots of U0105 helps to streamline diagnosis and repair. Below are the most common causes, ranked from most to least frequent:

Electrical wiring or connector faults: Damaged, corroded, or loose wiring/connectors between the ECU and the injector control module are among the primary reasons for communication failure.
Faulty injector control module: An internal fault within the module itself, such as a hardware malfunction, can result in no communication.
CAN bus network issues: Problems with the vehicle’s Controller Area Network (CAN bus), such as shorts, open circuits, or damaged wiring, can disrupt communication.
ECU (Engine Control Unit) software or hardware fault: Rare but possible, faults within the ECU affecting its communication capabilities.
Aftermarket or recent repairs: Incorrect installation, incompatible parts, or improper wiring during repairs or modifications can trigger this code.

How to diagnose trouble code U0105

If you encounter U0105, follow these generic steps to confirm and locate the problem:

Visual inspection: Check all wiring and connectors leading to the injector control module for damage, corrosion, or disconnections.
Check for other DTCs: Scan the vehicle for additional fault codes that may offer clues about related issues.
Inspect the fuse and relay: Verify that all related fuses and relays are intact and functioning properly.
Monitor live data: Use a professional diagnostic scanner to observe communication signals between modules in real-time.
Perform continuity tests: Test wiring continuity and resistance in the communication lines, especially the CAN bus wires.
Inspect grounds: Ensure all ground connections are clean, tight, and free of corrosion.
Reproduce the fault if possible: Try to duplicate the problem to see if the fault appears under specific conditions.

Possible repairs for trouble code U0105

Based on the causes listed above, here are potential repairs—ranging from simple to complex:

Reconnect or replace damaged wiring or connectors: This is a basic repair that often restores communication. Professional service may be required for damaged wiring beyond simple connector issues.
Replace the injector control module: If diagnosed as faulty, installing a new or known-good module is necessary. This is a more advanced repair typically performed by professionals.
Repair or replace damaged CAN bus wiring: Involves extensive electrical diagnosis and repairs that require technical expertise.
Update or reprogram the ECU software: If the fault stems from software issues, a firmware update by a professional may resolve the problem.
Check and repair the vehicle’s grounding system: Ensuring proper grounding can often resolve intermittent communication faults.

Vehicles commonly associated with trouble code U0105 in Europe

The U0105 fault is seen across various vehicle makes, especially those featuring advanced electronic networks. In Europe, it is commonly reported in models from:

Volkswagen Group: including Volkswagen, Audi, Seat, Škoda | Engine families: TSI, TDI, EA888

BMW: especially models equipped with iDrive and advanced fuel management systems

Ford: newer models with CAN bus architectures

Mercedes-Benz: particularly vehicles with multiplexed wiring systems

While these are a few examples, the underlying issue affects a wide range of modern vehicles utilizing complex communication networks.

Frequent mistakes with trouble code U0105

When diagnosing U0105, technicians and DIY enthusiasts should be cautious to avoid common pitfalls:

Inadequate visual inspections: Overlooking small wiring damage or poor connections can lead to misdiagnosis.
Ignoring other fault codes: Multiple communication faults often coexist; neglecting these can hamper proper repair.
Jumping straight to module replacement: Replacing parts without proper testing may result in unnecessary repairs.
Improper software updates: Incorrect ECU reprogramming can cause further issues.
Overlooking ground issues: Poor grounding is a frequent cause of communication faults and often missed during quick inspections.

FAQ — trouble code U0105

Can this code disappear on its own? In some cases, if the issue is caused by temporary contact issues or software glitches, the code may clear after fixing minor problems. However, persistent faults will likely return until properly repaired.

Can I keep driving? While some vehicles may operate with this fault, it is generally advisable to limit driving until diagnosis is complete. Continued driving can risk further electrical issues or damage.

Why does the code return after clearing it? If the underlying mechanical or electrical problem persists, the code will likely recur. Frequent retriggering indicates that the root cause has not been fully resolved.