GENERAL INFORMATION (DIESEL PARTICULATE FILTER SYSTEM)


The Diesel Particulate Filter (DPF) system is used to adsorb and remove the Particulate Matter (PM) contained in the exhaust gas. The engine-ECU anticipates the amount of PM accumulated in the DPF through the input signal from each sensor.
If the PM accumulates more than the standard, the engine-ECU carries out the control that automatically regenerates the DPF under certain conditions to remove the PM. At the DPF regeneration, the DPF temperature gets high and high temperature exhaust gases are given off.

SYSTEM DIAGRAM




CONTROL OVER ANTICIPATING AMOUNT OF ACCUMULATED PM


Calculating the input signal sent from each sensor, the engine-ECU anticipates the amount of PM accumulated in the DPF. The anticipation method is as follows:
Anticipation by odometer
 Calculating travel distance through vehicle speed signal, engine-ECU anticipates that PM accumulates more than criteria when specified travel distance is accumulated from previous DPF regeneration.
Anticipation by difference in pressure
 Detecting difference in pressure before and after DPF through exhaust differential pressure sensor, engine-ECU anticipates amount of accumulated PM.
Anticipation by quantity survey
 Engine-ECU anticipates amount of exhaust PM based on operation conditions, which multiplying allows engine-ECU to anticipate amount of accumulated PM.

DPF REGENERATION CONTROL
The DPF regeneration has the forcible regeneration by M.U.T.-III and the automatic regeneration automatically performed while the vehicle is running. The automatic regeneration is performed under the following conditions:

  • Engine: after warm-up
  • Vehicle speed: 40 km/h or more
  • Amount of accumulated PM exceeds specified value.
Performing the optimum engine control for the DPF regeneration, the engine-ECU increases the temperature up to the point at which the DPF regeneration can be carried out, and then keeps the temperature to burn the PM.

1. Rising Temperature Control
Performing rising temperature control having two steps, the engine-ECU increases the temperature up to the point at which the DPF regeneration can be carried out. At the first, the engine-ECU drives the variable geometry control solenoid valve and the throttle valve control servo and then performs the fuel injection with the optimum injection pattern, decreasing the intake air amount. This allows the high temperature exhaust gas to discharge as well as allows the catalyst in the front of the DPF to be heated to about 200°C, resulting in the catalyst activated, which is monitored by the No. 1 exhaust gas temperature sensor.
After the catalyst is activated, the engine-ECU performs the fuel injection called "post-injection" having more retarded timing than the usual timing. This allows the oxygen to react, in the catalyst, with the HC contained in the exhaust gas as well as allows the exhaust gas temperature to reach about 600°C at which the DPF regeneration can be carried out, which is monitored by the No. 2 exhaust gas temperature sensor (catalyst temperature).

2. Regeneration Control
When starting to perform the DPF regeneration, the engine-ECU carries out the feedback control so that the temperature in the DPF can stabilize at about 600°C through the output signal of the No.3 exhaust gas temperature sensor (DPF temperature). Controlling the injection amount of the post-injection and the intake air amount regulates the temperature in the DPF.
When being out of the regeneration condition during the automatic regeneration, the DPF regeneration stops. If, however, satisfying the regeneration condition right after that, the DPF regeneration is continuously carried out.

No. 1 EXHAUST GAS TEMPERATURE SENSOR, No. 2 EXHAUST GAS TEMPERATURE SENSOR (CATALYST TEMPERATURE), No. 3 EXHAUST GAS TEMPERATURE SENSOR (DPF TEMPERATURE)

The No. 1 exhaust gas temperature sensor is installed to the upstream area of the catalyst, the No. 2 exhaust gas temperature sensor (catalyst temperature) is installed to the downstream area of the catalyst and the No. 3 exhaust gas temperature sensor (DPF temperature) is installed to the downstream area of the DPF. Each sensor detects the temperature in the each area through the change in the thermistor resistance and outputs the voltage to the engine-ECU in accordance with the temperature. The engine-ECU performs the DPF regeneration control through this output voltage. The sensor characteristics are as shown in the charts.


EXHAUST DIFFERENTIAL PRESSURE SENSOR

The exhaust differential pressure sensor is installed to rear end of cylinder head cover, the exhaust differential pressure sensor outputs the voltage to the engine-ECU in accordance with the difference in the voltage between the DPF upstream area and the DPF downstream area. The engine-ECU anticipates the amount of PM accumulated in the DPF through this output voltage. The sensor characteristics are as shown in the charts.


DPF WARNING SIGNAL

When the anticipated PM accumulation becomes larger in amount and reaches the specified level, the engine-ECU encourages the driver to drive under the driving conditions required for the DPF regeneration by showing the DPF warning mark on the multi information display. When the PM accumulated in the DPF reaches its clogged or damaged level, the engine-ECU warns the driver that the vehicle must be brought to the workshop by showing the DPF warning mark in the multi information display. When the vehicle is brought into the shop with the DPF warning mark shown, service the vehicle in accordance with the following procedures.
DPF warning indicator
Engine warning lamp
 State and service
Illuminate
 Being lit
 The engine-ECU estimates that the PM will excessively be accumulated in the DPF.
At that time, the engine-ECU should set the diagnosis codes (P1498 and P2463). Carry out the troubleshooting regarding the set diagnosis codes (Refer to GROUP 13C - Troubleshooting - Diagnosis Code Chart ).
note Diagnosis code P2463 should be set if the engine-ECU estimates that the PM will more excessively be accumulated after P1498 is set and the PM will reach the level where the DPF cannot be regenerated.
Illuminate
 Not being lit
 The status is that the driver is advised to drive the vehicle under the driving conditions in which the DPF automatic regeneration can be carried out because it is assumed that the PM is accumulated more than the specified value in the DPF. In this case, the DPF regeneration must be carried out using one of the following two methods:

  • After the engine warm-up, the vehicle must be driven at more than 40 km/h until the DPF warning indicator is extinguished. The driving time is approximately 20 minutes. It is all right that the vehicle or the engine stops during the driving.

  • The forcible DPF regeneration must be carried out (Refer to ).