Problem
 |
| Particulate
filter |
In
this post, we are going to talk about how the particulate filter (FAP) and the
additive system function and are verified in PSA (Peugeot and Citroën)
group vehicles with BOSCH EDC 16C34 engine management.
For this, we are going to have the assistance of the documentation provided by
the www.dis-net.com platform and take the Peugeot 308 1.6 HDI as an
example.
The particulate filter is a component that reduces pollution in vehicles
equipped with a diesel engine by filtering the solid particulates from
the exhaust gas.
Over time, the filter becomes blocked due to the accumulation of these
particulates, ash from the engine oil and other residues. By means of a process
called regeneration, the anti-particulate filter burns these residues
and thus increases its efficiency.
The regeneration of the particulate filter is controlled by the engine
injection unit.
This unit's software:
• Controls the post-injections required for the forced regeneration of the
particulate filter so as not to excessively increase consumption or impregnate
it with oil.
• Ensures the regeneration process is carried out at the optimum moment.
The engine control unit calculates the saturation of the particulate filter
depending on the use of the vehicle, for this it compares the vehicle speed
with the engine torque.
The back pressure sensor is a safety element that activates filter
regeneration if the calculations are wrong and the filter becomes saturated
earlier than predicted.
The accumulated particulates can burn naturally when the optimal
temperature (approximately 500° C) is reached due to a heavy engine load for
three minutes.
If the above conditions are not met, the engine management system is capable of
assisting regeneration by acting on the following points:
- Increase of the electrical consumption of the vehicle: this is intended to
increase the resistant torque of the alternator, and thus increase the torque
and temperature of the engine.
- The heated rear window, the electric fan at the lowest speed, electric fan at
medium speed and the glow plugs are the electrical loads that are activated (in
that order).
- Overriding of the intercooler by means of the double throttle air
doser: the reduction of the aspirated air density reduces the performance of
the engine and consequently increases the temperature of the exhaust gas.
 |
| Red:
Movement of air with regeneration / Blue: Without regeneration |
-
The engine management system carries out post-injections in order to increase
the temperature at the particulate filter inlet.
In order to facilitate the regeneration process and to save fuel in
post-injections, Eolys is added to the fuel (compound based on cerine). This
additive lowers the temperature at which the regeneration of the particulate
filter starts: from 550°C down to 450°C.
The additive system consists of an electric pump controlled by the engine
management unit which injects the cerine from its tank to the fuel tank by
means of an injector. The cerine is injected during each refuelling and the
injected quantity depends on the number of litres added during refuelling. It
is calculated each time the fuel cap is opened and closed (the cap has a built-in
presence sensor).
While the engine is running, the Common rail injectors inject the fuel
and cerine mixture. The fuel is burnt inside the engine while the cerine passes
through to the exhaust system and is deposited on the particulate filter to
facilitate its regeneration.
NOTE: To ensure optimal operation of the particulate filter and to prevent
its premature deterioration, engine oils must the used with a low phosphated
ash, phosphorus and sulphur content.
Fault symptom
-
The MIL comes on and the message "Anti-pollution system defective"
appears on the central screen.
- Anomalies during driving: Engine noise, jerking, lack of power, engine
stalling, etc.
- The vehicle is difficult to start.
First steps:
- Verify the user's complaint.
- The diagnostics machine may indicate the following fault codes:
P0470: Exhaust system back pressure sensor signal:Back pressure out of range on
starting.
P0472 / P0473: Exhaust back pressure sensor signal: Short-circuit to
ground/short-circuit to battery positive.
P1447: Exhaust system back pressure sensor signal: Particulate filter
clogged.
P1457: Particulate filter defect Particulate filter holed or missing.
P1490: Regeneration not completed: Regeneration demand too frequent.
P2031: Temperature signal from the rear of the catalytic converter:
Temperature implausible before starting the engine.
P2032 / P2033: Temperature signal at the rear of the catalytic converter:
Voltage too low / Voltage too high.
Possible causes
-
Fault in the exhaust gas recirculation (E.G.R) system.
- Obstruction of the particulate filter.
- Fault in the particulate filter back pressure sensor.
- Electrical connection problem.
- Particulate filter temperature sensor in poor condition.
- Fault in the additive system
Diagnostics
Clear all the faults and turn off the ignition for more than 20 seconds.
Start the engine again and drive the vehicle for about 20 minutes at a constant
speed of 80 – 120 km/h in order to carry out a complete regeneration of the
particulate filter. Try to reproduce the symptom so that the previously stored
fault reappears to validate it.
Check that the joining hoses between the back pressure sensor and the particulate
filter are not damaged or obstructed.
Check the back pressure sensor is operating correctly, to do this proceed as
follows:
 |
Electrical
diagram of the Peugeot 308 1.6 HDI injection system
(www.dis-net.com) |
• Check the 5 V power supply between pins 2 and 3 of the sensor with the
ignition on.
• Check that there is a voltage of 0.5 V at pin 1 with the engine stopped (this
indicates a back pressure of 0 bar) (if this is not the value given, replace
the back pressure sensor).
• Start the engine and diagnose the condition of the particulate filter with
the voltage reading:
• From 0.4 V to 1.0 V means that the particulate filter is in good condition.
• 4.1 volts corresponds to 0.9 bar of back pressure, i.e. the particulate
filter is fully blocked. (Carry out the tests at different engine speeds, and
if necessary replace the particulate filter and encode it with an appropriate
diagnostic unit).
Check that the particulate filter temperature sensor is operating
correctly.
 |
| Particulate
filter temperature sensor |
The resistance of the NTC
(Negative Temperature Coefficient) sensor reduces as the temperature increases.
There are two different
ways of checking that it is operating correctly:
• By observing a reduction in voltage as the temperature increases (measure
between pins 1 and 2 of the sensor, without disconnecting it).
• By measuring its resistance (measure between pins 1 and 2, with the sensor
disconnected).
Check the particulate filter additive level and check the additive
system.
To check the additive level, remove the container located under the car,
(normally at the height of the left rear wheel).
If refilling is required, the type of additive can be identified by the colour
marked on the filler tube connector:
•Blue -> EOLYS POWERFLEX
•Green -> EOLYS 176 or INFINIEUM F7995
It is important not to mix them, if they are, the particulate filter will
age prematurely.
Reset the fuel additive calculator after each filling.
Check the additive pump. For this, activate it with an appropriate diagnostic
unit. Then listen for its operation and control its flow rate (50 sec à 20±5ml) (decouple the additive pipe from the tank and couple a suitable
container).
Check the additive injector operates correctly: disconnect the pipe that comes
from the additive tank and couple a manual pressure pump. The injector must
open at a pressure of 200 ± 40 millibar and withstand a vacuum of 800
millibars.
If these values are not complied with, replace the injector.
