What a catalytic converter is and what it does in a car, almost every car owner knows. However, there is some popularly repeated information about it that is not entirely true. As in almost everything, some people’s opinions must be treated with a wink. Even more so when it is their opinions or information come from an uncertain source. The catalyst in the car facts and myths – it’s worth to know them.
The catalyst in the car – facts and myths
Speaking about its assumptions and main functions, it should first be clarified who invented the catalyst in gasoline engines. Very often the information that can be found on this subject is that in 1989 Opel came up with such an idea. Unfortunately, this is not true, and the Opel brand itself simply claims the credit.
In fact, American scientists working in the 1960s and 1970s are responsible for this. It all began with the technological development that flourished after the Second World War. The American and European market is affected by the mass of cars that are becoming commonplace. Such an increase was increasingly felt by the environment.
Research has shown more and more harmful substances in the air, so they began to develop ways to reduce them in exhaust gases. California was one of the first states in the US to introduce regulations that oblige manufacturers and users to have a catalyst in a car.
In the beginning – the myths
The catalyst is a container for impurities
It is a mistake that the catalyst is considered a container for storing unnecessary combustion products. Depending on the catalyst, it has a ceramic or metal insert. There are important elements such as rhodium, platinum or palladium, which react chemically with oxides emitted from exhaust gases. As a result, they are oxidized, and therefore the exhaust gases are cleaned. In diesel engines, the catalyst oxidizes hydrocarbon and carbon dioxide, and then, for example, the DPF filter takes over the role of purification.
Can LPG “kill” the catalyst?
Of course not! Another myth to refute. Gas installation, e.g. sequential, which is very well regulated and tidy, does not affect the catalyst in any way. Catalyst damage can occur when the installation is poorly assembled or the flat is too poor. However, it should be said that such situations occur everywhere.
The catalyst blocks exhaust gases and reduces the car’s performance
Will the horsepower in the car increase thanks to the cut-out catalyst? Myth. It was created in the 1980s when older cars had catalysts that to some extent paved the way of exhaust gases. If the car has one lambda probe in front of the catalyst, it is possible that its cut out will result in a smoother passage of exhaust gases. However, this applies only to older models. In the event that the system may have more probes after the catalyst, the only thing you get is the information “check engine”.
The last myth worth mentioning is that you can’t remove the catalyst in the OBD II diagnostic system. This assumption is that this system has two lambda probes, so do not cut the catalyst. This is a wrong assumption, if only because the OBD I system may also have two lambda probes. Therefore, it is not worth following it and blindly assume that a car with OBD I system does not have two probes.
Now it’s time for the facts
If the catalyst has a ceramic insert, it may be damaged after long driving or hitting a deep puddle. This is not a common situation, but it has to be honest that it can happen.
Another fact about the catalyst is that its clogging can stop the engine. If the ceramic insert breaks down and the system becomes clogged, the car will not start. While in gasoline engines with slow suction, even a half-clogged catalyst does not show this by power drops, engines equipped with turbocharging react differently. Even a slight clogging will affect the visible loss of horsepower. This is an important symptom. An unnoticed fault for a long time can affect the overall condition of the engine.
Catalyst and ignition system
It is also true that the catalyst may be damaged by neglecting the ignition system. The contribution is quite delicate, therefore all self-ignition and traditional exhaust pipe shooting do not work well on the life of the catalyst. During the bad work of the computer, which has bad fuel and air doses, the catalyst can be seriously damaged. Similarly, it applies to start a car “on a push”.
What to do if the catalyst is damaged?
Once you know that the catalyst has broken down, you have several options to choose from.
1. cutting it out of the exhaust system, welding it, and then inserting a spotlight or can in its place
2. buying a catalyst from the secondary market
3. buying a universal catalyst, dedicated to the given power and a given version of the engine
4. purchase of a replacement dedicated to a given model
The first two options are illegal, harmful or highly risky. A catalyst used is not guaranteed, you are not sure what is inside and how it is handled. The next two options are cheaper than the original parts from an authorized service centre.
It is assumed that the most complicated system in a car is the engine and electronics. You can not disagree that modern cars in no way resemble those of years ago, and the amount of automation is amazing. However, the exhaust system has always been underestimated. What’s more, it is the most often perishable system because it works in extreme conditions. The most common muffler problems, which occupies a leading place among spare parts, are the result of mechanical (curbs, stone and gravel chips), physical (wide range of temperatures from very high inside to low outside) and chemical (rust, road salt).
Nothing is forever, but it requires prompt diagnosis
Each part of the car has a factory-specified optimal wear time given in months or thousands of kilometers traveled. The average life of exhaust components is:
muffler – an average of 2 to 6 years, brand new up to 10 years
catalyst – an average of 50-100 thousand km, brand new up to 200-300 thousand km
DPF filter – on average 120-250 thousand km
exhaust manifold – ??
lambda probe – an average of 50-160 thousand. km
Usually only one part breaks. However, ignoring the defect for too long can affect other parts of the exhaust system. That is why it is best to go to the car workshop as soon as possible.
The main tasks of the muffler
The basic tasks of the muffler are:
ensuring optimal engine operation
flue gas evacuation
- noise reduction
- gas reduction
Each car produces, among others, carbon monoxide while driving. It is flammable and explosive when combined with air. If it gathered under in the car, it would be too dangerous for users also due to poisoning. The muffler pushes carbon monoxide and other gases under the vehicle, ensuring safety and clean air in the cabin. This key part of the exhaust system is also responsible for the pressure control necessary for the proper operation of the engine.
Depending on the model, there are two or three silencers connected in series – front, middle and end rear. The first (from after the engine) is an absorption silencer with low exhaust gas flow resistance. Mutes high sound frequencies because the tube is hidden in a can filled with sound-absorbing steel or glass wool. The second order one is the chamber silencer, which is responsible for reducing low sounds. Otherwise, it is called reflective and in turn has high resistance to exhaust gas flow. It is built of a number of chambers of various sizes that connect the pipes.
The noise coming from the engine, along with the vibrations, is significant. The muffler allows quiet and pleasant driving. It is responsible for the comfort of the driver, passengers and the environment. At the same time, the tremor does not translate is not transferred into a body.
The most common muffler problems – damaged muffler symptoms
When a leak appears in the muffler, exhaust gases will not only appear outside the exhaust system, but in worse cases also in the cabin. They are sucked in by the air from under the car. The first symptom is a suffocating smell, in more drastic cases also smoke. The noise level may also increase depending on which damper muffler has been damaged. However the noise, it will not be as big as at a hole in the exhaust pipe.
A less obvious symptom is the mechanical tearing or denting of the muffler or smaller elements such as hangers, seals, clamps or fixing bands. What every driver will definitely feel is a significant drop in engine power, throttling while driving, acceleration problems and low maximum speed. At the same time, combustion will increase quite significantly. This is due to some of the exhaust gas receding into the combustion chamber and an inefficient process. It may also indicate that the absorption silencer is clogged with cotton wool, which enters the main pipe through perforations.
The most common muffler problems – self-diagnosis
The easiest way to locate a leak is to clog the exhaust pipe with a towel to a depth of about 10-15 cm. If the sound does not change, it indicates a hole. Going from the exhaust pipe, we are looking for a place where exhaust fumes are emitted or smoked. We can plug it with a rag, then we should get a different sound and a larger amount of exhaust gas coming out of the outlet. However, there may be more leaks, so it’s better to find them all.
The most common muffler problems concern the end muffler, where the steam condenses, so faster corrosion occurs. However, the location of the entire exhaust system in the chassis causes its faster wear off. Road salt and moisture also attack fasteners. Therefore, pay attention to the ends and connecting pipes.
If the muffler it is clogged, check the temperature of the parts. The cold one is probably clogged. However, be careful because the gases after leaving the engine are around 800 degrees C, and at the outlet about 200-300 degrees C.
In the first article, we described what diagnostic trouble codes (DTCs) are and how they work. We gave practical examples of how to use them to diagnose the exhaust system. Here we will present the most popular examples of DPF error codes related to other failures. In the second part, you can familiarize yourself with error codes related to sensor faults.
P242F – DPF limitation – ash accumulation
Ash in the DPF filter is a product of the use of lubricating additives for engine or diesel oils as well as impurities resulting e.g. from corrosion or general engine wear. It settles in the DPF filter on the walls or in its back, and thus blocks its capacity. The soot can be burned off in the process of automatic regeneration. On the other hand, the ash can only be removed by washing or replacing the DPF.
The P2424F code will be issued in one of the cases:
- actual clogging of the DPF filter – be it ash or unburned other sediments, which in turn indicate ineffective self-regeneration
- the use of engine or diesel oil not adapted to the exhaust system with a DPF filter
- damage to the sensor or its circuits due to their opening or short circuit, breaking of the sensor cables
In addition to the P242F code, the board indicator light (MIL) may also come on.
P2463 – DPF limitation – soot accumulation
Ash is not the only product of combustion. The DPF also accumulates soot, which, fortunately, can be burned during self-regeneration. Its frequency is regulated by a pressure sensor that compares the outlet values with those programmed by the manufacturer. Excessive soot that has not been burned regularly can result in sending code P2463. It may also indicate a malfunction of the regeneration process, a damaged sensor or its wiring.
There may also be other causes, e.g. diesel exhaust oil of poor quality or in insufficient quantity. Ultimately, during the diagnosis, a defect on the computer or its software can be suspected.
Regardless of what has failed, this is one of the most serious mistakes to look at carefully. Otherwise, further damage to the exhaust system or even the engine itself may occur.
P244A – DPF differential pressure too low (Bank 1) / P244B – DPF differential pressure too high (Bank 1)
The outlet pressure sensor in the DPF filter not only has to check its degree of filling. It also detects filter removal or malfunction. When the outlet pressure is too low or the pressure difference too high, the code P244A or B and the MIL lamp are activated. Automatic regeneration is suspended.
Removing the DPF filter is just one of the reasons. The DPF filter and the pressure sensor can be damaged as well. The code will indicate a leak in the sensor cable or an exhaust gas leak before or near it. It also disturbs the pressure value.
P2458 – DPF regeneration time / P2459 – DPF regeneration frequency
During the automatic regeneration of the DPF filter, the exhaust gas temperature increases, which facilitates burning of soot and carbon deposits. In order for it to occur, the engine must maintain increased RPM for min. 15-30 min. However, with urban driving style and too short time at higher revs, self-regeneration is not complete. As a result, the filter is still clogged. As a result, the computer reads the discharge pressure outside the norms.
Incorrect regeneration time can be caused by a defective filter, pressure sensor or short circuit in the electric circuit. Other reasons are bad or too little fuel exhaust fluid. It is also possible that the on-board computer or its software has been damaged.
Regeneration of DPF must take place not only for a limited time, but also with appropriate regularity, guided by the pressure sensor readings. All causes that cause the P2458 error code can also trigger the P2459 code. Self-regeneration usually takes place every 300-600 km, but when it is interrupted, the DPF will not reach sufficient throughput. Therefore, it will have to be repeated more often.
Examples of DPF error codes – summary
Most often, the malfunctions that display the error codes associated with the DPF filter and this section of the exhaust system are associated with a clogged filter or sensor malfunction. When diagnosing, you cannot rule out leaks in the system or short circuits in the electrical circuits. Not even malfunction of the diagnostic computer.
Some of the errors result from the selection of unsuitable or poor quality consumables, e.g. engine or diesel oil, or simply from wear. Some of them are soft code and are canceled after resolution of the cause and subsequent measurement.
The lighting of the DPF indicator on the dashboard should be a sign for any driver who needs a longer ride at increased speed to complete self-regeneration. If this does not help, it is necessary to go to the diagnostic station and read the error codes from the computer.
See also the second part with the codes P0470, P2002, P2003, P2031-36, P2452, P2453, P2454 and P2455.
In the previous article, we described what diagnostic trouble codes (DTCs) are. You could read there also how they work, and how to use them to diagnose the exhaust system. Here we will present the most common examples of DPF error codes related to sensor faults. In the second part, you can read the error codes related to other failures.
Error codes can be divided into “soft” and “hard”. Soft codes react to the current state of the car and if it changes, they automatically disappear. Hard codes indicate a problem until they are repaired and manually canceled using a scanner.
P0470 – Flue gas pressure sensor fault / P0471 – Flue gas pressure sensor range / performance fault
When the pressure in the intake manifold does not match the value transmitted by the exhaust pressure sensor, error P0470 or P0471 is shown. The value can also be compared to the air pressure around when the key is in the ignition.
The reason can be related to the electrical circuit or the breakdown of the exhaust pressure sensor itself. In very rare cases, the powertrain control module (PCM) may fail.
Much more often the causes are mechanical. The pipe between the exhaust manifold and the pressure sensor has been clogged or has leaked from the exhaust gas recirculation (ERG) system, e.g. with a leaking valve. Also, the air inlet or charge air inlet could leak.
Ignoring the cause of the error code may in turn result in clogging the DPF filter and the P242F code.
P2002 – DPF Performance Below Threshold (Bank 1) / P2003 – DPF Performance Below Threshold (Bank 2)
There are pressure sensors on both ends of the DPF filter. Deviations from the norm will be marked with error P2002 or P2003. They indicate that the filter is clogged and are also signaled on the dashboard. They are one of the soft codes. After successful self-regeneration of the filter and pressure return to normal, they disappear.
The cause is usually a clogged or damaged filter. Fuel with a high sulfur content or non-C or LowAsh engine oil increases the amount of carbon deposits, sediments and ashes, and thus clogs the filter and hinders its self-regeneration. Another reason for displaying the code is an air leak that changes pressure and sensor readings. Most often these codes appear when the car is not able to self-regenerate through urban driving style and driving short distances.
Ignoring the code may result in completely clogging the DPF and reducing the exhaust system performance.
Flue gas temperature sensor circuits 1st order sensor 2 (P2031, P2032, P2033) and 2nd order sensor 2 (P2034, P2035, P2036)
The exhaust gas temperature sensor (EGT) is fitted on most cars. Its task is to monitor and regulate exhaust gas temperature. Thanks to this, the DPF does not get too hot air (it could damage it) or too cold (it would prevent automatic regeneration).
The sensor can cause an error due to its own defect or mechanical damage to the parts of the exhaust system in its vicinity – loose connectors, terminals, their corrosion, cable damage or lack of insulation. No reaction from the mechanic side on these errors can be costly. DPF clogs without self- regeneration or damages when overheated.
P2452 – DPF a Pressure Sensor Circuit A / P2453 – Range / Performance of the DPF Pressure Sensor Circuit Range
On some cars, the pressure sensor is installed in the engine compartment, not the DPF. Hence, the measurement is made at a distance from the filter. The device itself is referred to as sensor A. Similar to the traditional construction of the exhaust system, pressure deviations from the manufacturer’s standards are signaled by an error code and lighting of the control lamp.
Some of the reasons for these codes are also similar – damage to the sensor or electrical circuit, clogged sensor cables, inefficient self-regeneration or filter clogging. A different location also gives some other ideas for diagnosis. The exhaust fluid tank is empty or flooded with bad fluid. When replacing the filter, the code may indicate the incorrect connection of a new element.
P2454 – DPF A pressure sensor circuit low / P2455 – DPF A pressure sensor circuit high
The pressure sensor A may be damaged while the DPF is operating normally. Then it will show too low result. Usually, the failure is related to a broken cable or broken electrical circuit, e.g. a short circuit or an interruption. However, you must also take into account the possibility of exhaust gas leakage.
However, be careful with code P2455 as it may damage the exhaust system or engine. Too high pressure readings can have the same causes as for code P2454. But, in addition, you must take into account the possibility of:
- damage to the DPF,
- lack of self-regeneration,
- empty exhaust fluid tank
- or its wrong mixture.
See also the third part of article with codes P242F, P2463, P244A and B, P2458, P2459.
An ordinary car user with a DPF filter will never have to deal with DPF error codes. A mechanic is different matter. For him, diagnostic trouble codes (DTCs) are a mine of knowledge, what is wrong with the car or its subassemblies. When internal sensors detect an abnormality or deviation from the norm, they transmit the code to the on-board computer diagnostic system (OBD).
Types of DTC error codes
Everything in the world tends to standardize. The international standards SAE and ISO have been in force since 2000 for car manufacturers, which unify OBD codes (the European version is EOBD). Therefore, the mechanic, independent of the manufacturer or the vintage, knows immediately what the defect is about.
Each code consists of five characters. The first letter symbolizes the location of the failure, the first digit says whether it is a generic fault or manufacturer fault.
B – body
C – chassis
P – engine
U – communication system
The next three digits are responsible for the location in a particular car system and the type of error. For example in code P:
0, 1 and 2: for the air/fuel mixture
3 : for the ignition system
4 : for checking auxiliary emissions
5 : for engine idling
6 : for the onboard computer and ancillary outputs
7, 8 and 9: for the transmission (gearbox)
- A, B and C : for hybrid propulsion
Is the DTC error code a full diagnosis?
The DTC error codes is just the beginning of the diagnosis. It should be verified with the vehicle’s operating instructions, because some codes (P1) are sometimes specific to the manufacturer.
When the diagnostic system indicates a component failure, check several components. The sensor itself, which sends false data or its cabling, could have been damaged. When the sensor is functional, it is necessary to see the whole sequence of the system. It is possible that a part has been broken which affects further elements and the DTC error code applies to the latter. For example, a dirty air flow sensor affects fuel-trim adjustments. In this situation, the air sensor will indicate problems with the fuel mixture.
DPF error codes
Also, each of DPF error codes can have many causes and therefore each case must be considered individually.
We have included specific codes in a separate article. There is no one, top-down and always working procedure. The repair is based more on the mechanics’ experience and diligence. A entire exhaust system is quite complicated and it is not always possible to clearly indicate what and why it failed.
The first step should be to look through technical service bulletins (TSBs) for a specific car model. Certain errors are popular and manufacturers make commonly available corrections. This will help you save time when diagnosing.
If this does not help, look at the exhaust system thoroughly, not just the DPF filter itself.