Code U0118 indicates that the vehicle's primary control module has lost communication with the Fuel Additive Control Module. This means the network can no longer send or receive data from the system responsible for managing fuel additives or diesel exhaust fluid.
Internal electronic failure within the module prevents it from communicating on the CAN bus.
Chafed, broken, or rodent-damaged wires interrupting the communication signal between modules.
A loss of power to the additive control module prevents it from booting and communicating.
Moisture or salt intrusion at the module pins causing high resistance or a complete open circuit.
A short or open in the vehicle's data network affecting multiple modules.
A failure in the PCM's communication gateway, though this is significantly less common than module or wiring failure.
Not necessarily. U0118 is a communication code, meaning the computer cannot 'talk' to the module. While a module failure may stop the pump, the pump's mechanical failure usually triggers different, specific component codes.
No. It is very rare for the PCM to be the cause of a single-module communication loss. The failure is almost always located in the additive module itself, the wiring, or the power supply.
In many diesel vehicles, communication loss with the additive system will eventually trigger a 'no-start' condition after a predetermined amount of driving distance to ensure emissions compliance.