U0105 Code: Lost Communication With Fuel Injector Control Module
The PCM lost contact with the separate module that fires the injectors, common on diesel pickups.
Stop driving
If the engine is misfiring, smoking or stalling, don't keep driving; unburned fuel washes down cylinders and a stall on the highway is dangerous. If it starts and runs cleanly after a single event, get the batteries and module tested before relying on the truck.
At a glance
Severity: High
- Meaning
- Lost Communication With Fuel Injector Control Module
- System
- Module Communication · Network
- Safe to drive?
- With caution
- Typical repair cost
- $150–$1,600
- DIY difficulty
- Moderate
Most engines fire their injectors straight from the PCM, but some, especially diesel pickups, use a separate fuel injector control module (FICM) or injector driver module that boosts battery voltage to a much higher level to snap the injectors open quickly. The PCM decides timing and quantity and sends commands to that module; U0105 means the PCM stopped hearing back from it. The best-known example is the Ford 6.0L Power Stroke, whose FICM sits on top of the engine and turns 12 V into roughly 48 V; heat cycling and chronically low battery or alternator voltage kill its power supply section. Because the injectors can't fire without the module, the result ranges from hard starting and misfire to a crank-no-start.
How to read U0105
- U Network
- 0 Generic (SAE)
- 1 Module Communication
- 05 Specific fault
Symptoms
- Long crank or no-start, worse when cold
- Rough idle, misfire or white smoke after start-up
- Engine dies or stumbles under load, then restarts
- Check engine light with injector circuit codes alongside U0105
- Scan tool can't open the injector module or shows its voltage as zero
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Weak batteries or charging voltage starving the module (diesels with two batteries are especially sensitive)
- Failed power-supply section inside the injector control module from heat cycling
- Loose, corroded or oil-soaked connector at the module or injector harness
- Blown fuse, bad relay or poor ground feeding the module
- Damaged CAN or signal wiring between PCM and module
- PCM fault or software mismatch after a module swap
Diagnosis step by step
Test both batteries and charging
Each battery should rest near 12.6 V and pass a load test, and the engine-running voltage should sit between about 13.8 and 14.6 V. On dual-battery trucks one bad battery drags the other down; test them separately.
Tools: Multimeter
Check module power, ignition feed and ground
Back-probe the module connector: battery voltage on the main power and logic power pins with the key on, and a ground with under about 0.1 V drop while cranking. Measure while cranking, because a supply that collapses under load won't show with the engine off.
Tools: Multimeter
Read the module's output voltage
On modules that report it, a capable scan tool shows the injector supply voltage (about 48 V on the Ford 6.0L); a reading that sags well below spec while cranking indicates a failing power supply. Otherwise measure it at the specified test point.
Tools: OBD-II scanner, Multimeter
Inspect connectors and harness
Look at the module's connectors and the injector harness for oil intrusion, burnt pins and loose locks. Engine-mounted modules get heat-soaked, so wiggle-test the harness with the engine idling and watch for stumbles.
Tools: Flashlight
Verify CAN communication
Check CAN-high and CAN-low at the module for about 2.6 V and 2.4 V with the key on, and continuity back to the PCM with the battery off. Only after supply, output and bus wiring check out is the module itself condemned.
Tools: Multimeter
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace weak battery or batteries | Yes | $180–$500 |
| Repair module connector or harness | No | $150–$450 |
| Rebuild or upgrade the module power supply (exchange service plus labor) | No | $350–$800 |
| Replace fuel injector control module and program | No | $700–$1,600 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Ford
The 6.0L Power Stroke (Super Duty and E-Series) is notorious for FICM failures; low battery voltage and heat are the usual killers, and rebuilt units with upgraded power supplies are a common fix. The earlier 7.3L uses a similar injector driver module mounted on the inner fender.
Field data
| Toyota | 2 | RAV4 |
|---|
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
U0105 turns on the check engine light and disrupts combustion, so it fails a US emissions test. Diesel pickups over the weight limit are exempt in some states, but any state that reads OBD will reject it.
Frequently asked questions
Why does a weak battery kill the injector module?
The module converts 12 V into a much higher injector voltage. When input voltage is low, its power stage works harder and runs hotter, which is what eventually burns it out. Healthy batteries are the cheapest protection.
Does my gas car even have a fuel injector control module?
Most don't; the PCM fires the injectors directly. On those vehicles U0105 is uncommon, and the service information should be checked to see which module the manufacturer means.
Can I just replace the module myself?
On many trucks the module bolts on the engine and is physically easy to swap, but it may need programming to match the PCM. Test the batteries first, or the new module can fail the same way.
Will U0105 damage the engine?
The fault itself isn't destructive, but running with misfires can wash fuel into the oil and overheat the exhaust aftertreatment. Don't drive it long in that state.
Sources
- SAE J2012 – Diagnostic Trouble Code Definitions
- ISO 15031-6 – Road vehicles, diagnostic trouble code definitions (EOBD)
- Manufacturer public service information (cross-checked)
- NHTSA Complaints API
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