| Fault Code | Description | Likely Cause | |------------|-------------|----------------| | | RFC – Additive level too low | Additive tank empty or level sensor failure | | 4742 | RFC – Additive dosing circuit malfunction | Clogged injector, pump failure, or blocked line | | 4743 | RFC – Additive pressure sensor fault | Faulty pressure sensor in dosing unit | | 4744 | RFC – Communication error between ECU and RFC controller | CAN bus interruption, wiring issue, or faulty RFC module | | 4745 | RFC – Additive quality error | Wrong or degraded additive (non-genuine fluid) | | 4746 | RFC – Additive temperature out of range | Sensor failure or heater malfunction (cold climates) | | 4747 | RFC – DPF efficiency low due to missing additive | Additive system disabled or empty for long period | | SPN 5394 / FMI 0-16 (J1939) | RFC Additive Tank Level – Low / Data erratic | Level sensor or wiring short |

The RFC system is highly sensitive to resistance. Even using the (e.g., using a 21W where a 10W is required) can trigger a persistent RFC error. Ensure all rear position, turn, and license plate bulbs are intact and match OEM specifications. 2. Inspect the Chassis Wiring

For pressure-related RFC codes (like DTC 09), the sensor on top of the Air Processing Unit (APU) is a common failure point due to excessive air pressure. Wiring Harness:

Communicating power and signals to the trailer. Common RFC Fault Codes and Meanings

: A "soft reset" can be performed by disconnecting the battery for one minute, but recurring codes often point to a bad ground on the chassis sub-harness. Wiring Loom Sensitivity

Blown bulb or incorrect bulb wattage triggering a resistance error.