1 Fuel additive control unit
A separate fuel additive control unit is responsible for fuel additive injection. This is installed on the right-hand side of the passenger compartment under the rear seat.
It is connected to the PCM via CAN data bus. The fuel additive control unit detects when the vehicle has been refueled on the basis of various input values and subsequently controls metering of the fuel tank additives to be injected into the fuel tank. The fuel additive control unit also features a counter function. Using this counter, the fuel additive control unit calculates the liquid level in the fuel additive tank by recording the frequency with which the fuel additive pump unit is actuated and the duration of these actuations.
As soon as the level drops below a specific, calculated quantity remaining in the fuel additive tank, the engine system fault warning lamp in the instrument cluster is actuated, indicating in this case that the quantity of fuel additive remaining is sufficient for approximately 250 liters of fuel.
This means that in the case of a fuel tank with a capacity of 50 liters, sufficient fuel additive remains available for approximately five complete refueling operations or, for example, for ten refueling operations at 25 liters each.
Information concerning the actual quantity of fuel added is sent by the fuel level sensor. With a properly functioning system, only refueling quantities exceeding 5 liters are registered.
If the engine system fault warning lamp illuminates, this is a signal to the driver of the vehicle that he should drive to the nearest Authorized Ford Workshop as soon as possible. If this does not happen the MIL is set when the fuel additive tank has been emptied completely. To indicate an empty fuel additive tank, the fuel additive control unit sends the appropriate information via CAN data bus to the PCM, which logs a DTC and, in turn, actuates the lamp in the instrument cluster, also via the CAN data bus.
Note: If one of the previously mentioned lamps illuminates to indicate that the fuel additive tank is empty, the corresponding DTC must be cleared in the fault memory by means of WDS once the fuel additive tank has been refilled. In addition, the counter must be reset by means of WDS.
Note: The fuel additive tank cannot be emptied fully. Once the quantity remaining falls below 0.3 liters, fuel additive injection ceases (the driver is informed before this occurs by means of the relevant warning lamps).
The residual quantity prevents the fuel additive pump from drawing in air, which could result in incorrect quantities of fuel additive being metered.
Diagnosis
The fuel additive system is a stand-alone system controlled by the fuel additive control unit. The fuel additive control unit detects faults in the fuel additive system and sends these via CAN data bus.
The PCM registers the CAN fault data from the fuel additive control unit and subsequently logs a corresponding DTC.
Faults in the fuel additive system can lead to illumination of both the engine system fault warning lamp and the MIL.
In the event of CAN communication failure, the MIL is also actuated.
Possible diagnostic trouble codes: P2584, P2585, U0118