Ford Workshop Service and Repair Manuals

Principles of Operation

Fuel additive system overview

To reach the latest Stage IV emissions legislation, diesel vehicles require a system to clean the exhaust gases before they exit the exhaust system.

This is achieved by trapping or filtering the soot particulates produced during engine combustion. A diesel particulate filter is located in the exhaust system, downstream from the catalytic converter. The soot particulates coated with fuel additive, are stored in the diesel particulate filter until they reach a pre-defined level. At this point a process known as regeneration occurs.

Regeneration requires the exhaust gasses to be increased to approximately 500°C, much higher than typically obtained during general driving. The powertrain control module (PCM) uses control of the fuel and air systems to achieve this.

Regeneration is initiated at between 300-1000 km (186-621 miles) or earlier if the engine management system dictates.

The distance is dependent on the soot accumulation, which varies with the differing drive styles.

The remaining ash particles (which is a result of the regeneration of the soot particles and fuel additive) cannot be burnt and are collected in the diesel particulate filter. The diesel particulate filter is serviced every 120,000 km (74,000 miles) or earlier depending on vehicle drive cycles. For additional information,
REFER to: Exhaust System (309-00, Description and Operation).

The PCM will choose the optimum time to regenerate. Under normal operating conditions the regeneration process occurs when the PCM calculates that the diesel particulate filter requires regeneration and that a number of predetermined vehicle conditions are met (i.e. coolant temp, vehicle speed & load).

The PCM will then initiate the regeneration process by the following:

• closing the exhaust gas recirculation (EGR)
• increase the engine load
• regulation of the intake temperature and pressure through the intake air shutoff throttle
• additional fuel injections (post main fuel injection)

All these changes to engine behavior will increase the exhaust gas temperature. The increase in temperature will allow the soot particles and fuel additive in the diesel particulate filter to burn.

A calculated amount of fuel additive is injected into the normal fuel tank through a fuel additive injector located in the fuel tank, every time the fuel tank is refilled. The calculated quantity of fuel additive injected, is achieved by the fuel additive system module communicating on the central area network (CAN) bus circuit to the following components:

• fuel tank filler pipe cover switch and magnet
• PCM
• instrument cluster (fuel level)

The fuel additive system module calculates the required amount of fuel additive to be injected into the fuel tank and activates the integral dosing pump.

Some components have been modified or work in conjunction with the diesel particulate filter and fuel additive system to meet the emissions level such as:

• intake air distribution system
• EGR system

Vehicles with 1.6L Duratorq-TDCi (DV) diesel engine

Vehicles with 2.0L Duratorq-TDCi (DW) diesel engine

Diesel particulate filter

The diesel particulate filter element is a honeycomb structure in which the walls of the structure are made of porous silicon carbide (composition of carbon with metal). The individual ducts are sealed at one end of the element and offset at the other.

As the exhaust gases with the soot particles and fuel additive are filtered/forced through the porous walls (due to the offset sealed ducts), the soot particles and additive are stuck to the walls of the element. This process occurs until a large build up of soot particles and fuel additive attached to the porous walls increase the exhaust gas pressure before the diesel particulate filter, which is monitored by the pressure differential sensor for diagnostic purposes.

The regular regeneration of soot particulates stored in the diesel particulate filter leads to a build up of stored ash (by-product of the regeneration process). This build up reduces the usable volume within the diesel particulate filter which soot is stored between regenerations, thus shortening the regeneration interval (as calculated by the PCM). For this reason the diesel particulate filter must be changed at the scheduled service interval.

On vehicles with 1.6L Duratorq-TDCi (DV) diesel engine, the diesel particulate filter and catalytic converter are serviced as a complete unit, whereas on vehicles with 2.0L Duratorq-TDCi (DW) diesel engine , the diesel particulate filter is a separate component installed after the catalytic converter and is serviced as a separate unit.

Exhaust gas temperature sensor

The exhaust gas temperature sensor measures the temperature of the exhaust gases as they pass through the diesel particulate filter. The temperature of the exhaust gases must be approximately 500°C for the soot particles and fuel additive to be regenerated.

The exhaust gas temperature sensor will send exhaust gas temperature data back to the PCM. This will enable the PCM to calculate the thermal energy produced and allow it to verify whether a regeneration event has been either partially or completely successful.

Pressure differential sensor

The pressure differential sensor main function is to assist the diagnosis of the diesel particulate filter. It determines if the diesel particulate filter is in one of the following states:

• partially blocked
• completely blocked
• missing

The pressure differential sensor is connected to the diesel particulate filter by two pipes for monitoring the pre and post pressures of the diesel particulate filter. The pressure differential sensor converts the measurements taken from the two pipes into voltage, which is then sent to the PCM as part of the decision of whether to apply the regeneration process or not.

Intake air shutoff throttle - vehicles with 1.6L Duratorq-TDCi (DV) diesel engine

The engine is equipped with an intake air shutoff throttle, which acts as a charge air cooler bypass while the diesel particulate filter is being regenerated.

The intake air shutoff throttle redirects the air from the turbocharger outlet pipe to the intake manifold by closing the intake manifold air intake valve, using a stepper motor. This uncooled (warm) air is measured by the charge air temperature sensor during the regeneration process.

The introduction of the intake air shutoff throttle means the air mass directed through the charge air cooler is reduced throughout the regeneration of the diesel particulate filter and at the same time, the warm or uncooled air to the intake manifold increases, to allow for high temperature combustion, which burns the soot particles and fuel additive efficiently.

The volumetric efficiency of the engine is reduced due to the redirection of the air flow, while at the same time the intake air temperature is kept constant, to prevent fluctuation in exhaust gas temperatures during regeneration.

The intake air temperature is monitored by the charge air temperature sensor in the intake air shutoff throttle housing. If the air temperature reduces, the PCM will correct the intake air shutoff throttle to allow the temperature of the intake air to increase and remain constant.

Intake air shutoff throttle - Vehicles with 2.0L Duratorq-TDCi (DW) diesel engine

The intake air shutoff throttle equipped to vehicles with 2.0L Duratorq-TDCi (DW) diesel engine has the same operation as the intake air shutoff throttle on the 1.6L Duratorq-TDCi (DV) diesel engine, but with a difference in valve operation. These are controlled by vacuum operated valves instead of stepper motor controlled valves. The vacuum operated valves using remote control solenoids are controlled by the PCM, which open and close the valves during the regeneration process.

Fuel additive

The fuel additive uses a metallic catalyst consisting of cerium and iron. This allows the soot particles to be burnt off (regeneration) at a lower temperature.

When the fuel mixture (with the fuel additive) burns in the engine combustion chamber, cerium oxide (fuel additive) particles bind with the soot particles, which are then filtered by the diesel particulate filter and become embedded within the diesel particulate filter element.

The regeneration can accelerate the oxidation process considerably. due to the larger numbers of contact points between the cerium oxide particles or fuel additive and soot particles.

Fuel additive tank

The fuel additive tank is located to the rear of the fuel tank and is secured to the rear subframe.

The fuel additive tank has an integral dosing pump built into the side of the fuel tank and can only be serviced as a complete unit.
REFER to: Fuel Additive Tank (310-01, Removal and Installation).

The fuel additive tank has the capacity of 1.8 liters and a total driving distance to empty of 60,000 km (37,000 miles) and must then be refilled.
REFER to: Fuel Additive System Filling and Bleeding (310-00, General Procedures).
After the refill of the fuel additive tank, the fuel additive system module must be reset by using either WDS, or manually with the fuel filler door providing no diagnostic trouble code(s) (DTC)s are present.
REFER to: Fuel Additive System Service Reset Procedure Without Using Diagnostic Tool (310-00, General Procedures).

Fuel additive injector

The fuel additive injector is an integral part of the vehicle fuel tank and is connected to the fuel additive tank with a short length of fuel pipe. The fuel additive injector cannot be removed from the fuel tank and must be serviced as a complete unit.
REFER to: Fuel Tank - 1.6L Duratorq-TDCi (DV) Diesel/2.0L Duratorq-TDCi (DW) Diesel, Vehicles With: Fuel Additive Tank (310-01, Removal and Installation).

The fuel additive injector is a one-way valve that opens to allow the calculated fuel additive to be injected into the fuel tank. The one-way valve opens due to the fuel additive pressure created by the dosing valve in the fuel additive tank. The one-way valve closes once the pressure has dropped after the calculated amount of fuel additive is injected into the fuel tank.

Fuel additive system module

The fuel additive system module is located under the rear seat cushion.

The main purpose of the fuel additive system module is to calculate the required amount of fuel additive and control the time of injection into the fuel tank. It also stores DTC(s) for the fuel additive system.

In addition to the already mentioned operation of the fuel additive system module, the instrument cluster will receive a command from the fuel additive system module to illuminate the malfunction indicator lamp (MIL) or the powertrain warning indicator if there are concerns with the additive system or if the fuel additive tank requires refilling.

The fuel additive system module also counts the amount of fuel tank refills and fuel additive injections that have occurred and sends the information to the PCM.

The fuel additive system module must be reset after the fuel additive tank has been refilled or DTC(s) have been retrieved by connecting to WDS through the data link connector (DLC).

The following information shows the components connected to the fuel additive system module, that assist in the calculation and metering of the quantity of fuel additive added.

The fuel additive system module communicates with the PCM and instrument cluster by using the high-speed CAN bus circuit. The other components connected to the system are standard wiring harnesses.

Fuel filler door switch and switch magnet

The fuel filler door switch works in conjunction with the fuel filler door switch magnet to indicate to the fuel additive system module that the fuel tank is being refilled.

The fuel filler door switch is closed contact when the fuel filler door is opened. A signal is sent to the fuel additive system module to indicate that the fuel tank is being refilled.

The fuel additive system module goes into sleep mode while the fuel tank is being refilled. Once the refill has been completed, the fuel filler door is closed and the fuel filler door switch is open contact, which cancels the fuel additive system module sleep mode.

When the ignition key is turned to position II, the current fuel tank level is registered by the PCM and compared with the previous level (before the fuel tanks was refilled). The difference between the two measurements is then calculated. The information is then added to the fuel additive tank refill calculations for the correct quantity of fuel additive to be injected.

Dosing pump

The dosing pump has a main function of supplying the correct calculated quantity of fuel additive to the fuel tank. This is achieved by signals sent from the fuel additive system module to the dosing pump, regarding the pump operation duration.

The dosing pump has a piezo sensor for the following functions:

• The piezo sensor calculates the viscosity of the fuel additive which maybe affected by the ambient air temperature and transfers the value(s) to the fuel additive system module.
• The piezo sensor measures the fuel additive level in the fuel additive tank only at very low level and transfers that information to the fuel additive system module.

The fuel additive system module can calculate the inputs of the piezo sensor and determine the precise quantity of fuel additive to be injected into the fuel tank.

Concerns with the diesel particulate filter and fuel additive system

Due to the nature of the diesel particulate filter and the fuel additive system, some unusual vehicle behavior may be induced if the vehicle is driven on short or stop/start journeys. The diesel particulate filter needs to have higher temperature exhaust gases than the normal operating temperature to assist the regeneration process. Short journeys have the opposite effect. The soot particulates and fuel additive build up in the diesel particulate filter element becomes excessive and blocks the diesel particulate filter. Typical symptoms exhibited for this are as follows:

• Lack of power
• Poor engine performance
• MIL or powertrain warning indicator will illuminate.

Inspection and Verification

WARNING:Do not smoke or carry lighted tobacco of any type when working on or near any fuel related components. Highly flammable mixtures are always present and may ignite. Failure to follow these instructions may result in personal injury.

WARNING:This procedure involves fuel handling. Be prepared for fuel spillage at all times. Failure to follow this instruction may result in personal injury.

WARNING:Diesel fuel injection equipment is manufactured to very precise tolerances and fine clearances. It is therefore essential that absolute cleanliness is observed when working with these components. Always fit blanking plugs to any open orifices or lines.

CAUTION:Always carry out the cleaning process before carrying out any repairs to the fuel injection system components to prevent foreign matter ingress to the components.

Visual Inspection Chart

Symptom Chart

Symptom Chart

Pinpoint Tests