What Does U0118 Mean?
The powertrain control module (PCM) has lost communication with the fuel additive control module over the vehicle's communication network (CAN bus). This module controls diesel exhaust fluid (DEF) or other fuel additive systems.
Common Causes
35%
Faulty fuel additive control module
30%
Damaged or corroded wiring harness/connectors to fuel additive module
20%
CAN bus network fault or short circuit
10%
Low battery voltage or poor ground connection
5%
PCM software needs updating or PCM failure
Diagnostic Steps
1
Step 1: Check battery voltage (should be 12.4V minimum) and inspect all ground connections
2
Step 2: Inspect wiring harness and connectors to fuel additive control module for damage, corrosion, or loose connections
3
Step 3: Use scan tool to attempt to communicate directly with fuel additive control module and check for module power and ground
4
Step 4: Measure CAN bus high and low signals at fuel additive module connector (should see 2.5V nominal, varying between 2.0-3.5V)
5
Step 5: If no communication possible and power/ground are good, replace fuel additive control module
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The powertrain control module (PCM) has lost communication with the fuel additive control module over the vehicle's communication network (CAN bus). This module controls diesel exhaust fluid (DEF) or other fuel additive systems.
The most common cause of U0118 (Lost Communication With Fuel Additive Control Module) is: Faulty fuel additive control module
Typical repair costs for U0118 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may enter limp mode or experience reduced power. DEF system malfunction may prevent vehicle from starting after a certain time period per emissions regulations.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0118 to identify the root cause.
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Quick Info
Category
Network
System
Emissions Control / Fuel Additive System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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