U0118 code meaning
Lost Communication With Fuel Additive Control Module
Network system Generic code U01xx codes Check engine light
What U0118 means
U0118 concerns the fuel additive control module, which on some diesel cars meters a fuel-borne catalyst from a separate tank into the fuel. The additive lowers the temperature at which trapped soot burns in the particulate filter from above 600 °C to roughly 350–450 °C. If the engine controller no longer receives this module, it cannot be sure that dosing continues, and the regeneration strategy loses its footing. No manufacturer documents U0118 publicly; the text rests on CARB's requirement for a separate lack-of-communication code and on the known function of fuel-borne catalysts. Neighbours are U0467 (invalid data), P2584 (MIL request) and P2585 (warning lamp request) from the same module. Left unrepaired, the filter tends to clog, bringing a DPF warning and reduced power.
U0118 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0118
- MIL and particulate filter warning
- Regeneration fails, filter loads up
- Reduced power in later stages
Common causes of U0118
- Most likelyAdditive module unplugged or its fuse removed, e.g. after filter work
- PossibleCorroded connector at the additive tank or module under the vehicle
- PossibleDamaged CAN wiring to the additive module
- Less likelyFuel additive control module internally faulty or not coded
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel additive moduleCAN bus wiring
What each part of U0118 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 18 | The exact fault in that area. |
What to do next
- Note U0118 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0118
What does U0118 mean?
U0118 means "Lost Communication With Fuel Additive Control Module". U0118 concerns the fuel additive control module, which on some diesel cars meters a fuel-borne catalyst from a separate tank into the fuel. It is a generic code, so it means the same on every make.
Is it safe to drive with U0118?
Drive gently and only to a workshop. With U0118 the car can go into limp mode (reduced power) to protect itself.
Will U0118 fail an emissions test?
Yes, it can. U0118 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0118 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U0118 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.