Network, generic

U0118 Lost Communication With Fuel Additive Control Module

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Additive module unplugged or its fuse removed, e.g. after filter work
Corroded connector at the additive tank or module under the vehicle
Damaged CAN wiring to the additive module
Fuel additive control module internally faulty or not coded

Symptoms

  • MIL and particulate filter warning
  • Regeneration fails, filter loads up
  • Reduced power in later stages

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–900
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel additive modulecan bus wiring

Related codes

U0467P2584P2585U0100

References: law.cornell.edu, en.wikipedia.org.