U0118: Lost Communication With Fuel Additive Control Module
What to do
You will notice nothing at all, and that is exactly why this one gets ignored until it is expensive.
Your car carries a small tank of additive that is dosed into the fuel to help the exhaust particulate filter burn off its soot. This code means the computer that does the dosing has stopped talking to the rest of the car, so the dosing has stopped.
The engine will run the same, the economy will be the same, and nothing will warn you. What happens instead is that the filter gradually stops clearing itself, and blocks — months later, and expensively.
So book it in while it is cheap. Ask specifically for the wiring to the additive tank to be checked: the tank and its pump usually live under the car near the fuel tank or in a rear wheel arch, in the road salt and stone chips, so a broken wire is far more likely than a failed computer, and much cheaper.
And if the particulate filter is being replaced, insist the additive tank is refilled and its counter reset at the same time. A new filter fitted without that blocks again on exactly the same timescale.
What this code means
The fuel additive control module has stopped being heard from. The general reasoning is at U0100, and U0467 explains the fuel-borne catalyst system and why it matters months after this code appears.
This is one of the corpus's clearest cases of a fault with no symptom and a real bill attached.
Nothing changes when this module goes quiet. The engine runs identically, the economy is unchanged, there is no warning beyond the engine light and possibly not even that. What stops is the dosing — the tiny quantity of cerium or iron compound metered into the tank at each refuelling, which is what lets the particulate filter burn its soot off at temperatures it would otherwise never reach.
So the filter quietly stops regenerating properly, and blocks some months later. That is the whole content of this page, and it is why a code with no symptom should not be deferred.
One thing specific to silence rather than bad data. The additive tank and its metering pump usually sit under the vehicle beside the fuel tank or inside the rear wheel arch — road spray, salt and stone damage — so an open circuit here is very often the harness rather than the module, and it is a repair rather than a replacement.
And the standing warning from U0467 applies with force: if the particulate filter is replaced while this is unfixed, it will block again on the same timescale. The additive tank must be refilled and its counter reset as part of that job.
Likely causes
Start here
- Damaged wiring harness · moderate
- Corroded or loose connector · easy
- Water ingress into the module connector · moderate
Less common
- Physical damage from road debris · moderate
- Blown fuse or failed supply · easy
- Damaged data bus wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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