U0105
Lost Communication with Fuel Injector Control Module
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Code U0105 indicates that the powertrain control module has lost communication with the Fuel Injector Control Module (FICM). The FICM is responsible for delivering precisely timed electrical pulses to the fuel injectors, controlling when and how much fuel enters each cylinder. This code is especially common on diesel engines (such as the Ford 6.0L Power Stroke) where a separate FICM generates the high voltage needed to fire piezoelectric injectors.
When the FICM drops off the CAN bus, the engine may run very poorly or not start at all. Without communication between the PCM and FICM, the injectors cannot receive proper firing commands, leading to misfires, rough running, power loss, and excessive exhaust smoke. On vehicles where the PCM directly controls the injectors (without a separate FICM), this code is less common.
Start diagnosis by checking the FICM's power supply—these modules draw significant current and their fuses and connectors are prone to failure. The FICM connector pins should be inspected for corrosion, especially since the module is typically mounted in the engine bay where it's exposed to heat and moisture. If the power supply and wiring are sound, the FICM itself is likely faulty and will need replacement or rebuilding.
Severity
Symptoms
- •Engine running rough, misfiring, or lacking power
- •Hard starting or extended cranking before engine fires
- •Black smoke from exhaust indicating improper fuel delivery
- •Significant decrease in fuel economy
- •Check Engine Light illuminated, possibly flashing
- •Engine may stall at idle or under load
Likely Causes
The Fuel Injector Control Module is often mounted on or near the engine, exposing its wiring to extreme heat, vibration, and moisture. CAN bus wires in this harsh environment can become brittle, chafe, or corrode over time.
The FICM is subjected to significant heat from its location near the engine. Internal circuit board components can fail, solder joints can crack from thermal cycling, and the module's CAN bus transceiver can stop functioning.
The FICM requires robust power supply to drive the fuel injectors. A blown fuse, corroded power connector, or high-resistance ground will cause the module to lose its CAN bus connection and stop communicating.
A broader CAN bus issue on the network segment that includes the FICM—such as a short or open in the backbone wiring—can isolate the module. Additional U-codes for other modules on the same segment will typically be present.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Inspect FICM power supply fuses and relays, replace if blown
- Check and clean the FICM connector pins for corrosion, especially the power and CAN bus pins
- Test FICM power supply voltage (should be battery voltage) and ground connections
- Inspect CAN bus wiring between the FICM and the main harness for damage
- Replace the FICM if power, ground, and CAN bus wiring all test good