Performance tests of CO catalytic converters

Disclaimer, that the information available from the manufacturer is zero, corresponds this case for all 100%. All described below – my observation and a little research.


Experience shows that MSD80 (and also related DME of MSV/MSD series) measures the performance of CO catalytic converters driving evenly (with stable RPMs and requested torque).

There is no exact information, how the measurements of the performance of CO catalytic converters are done, but some simplest solutions could be:


Homogeneous mode:

a) during the test, Lambda is reduced to 0.98 for a short (a second or two) moment, and a small fuel leftover (2%) is thrown in the exhaust. After then the Lambda is increased to 1.02, and 2% of air is thrown in the exhaust. Using a control probe/probes – measuring the time while the oxygen is not detected in the exhaust;

b) maintaining the total Lambda of the bank correct (1.00), disbalance the fuel mixture of cylinders by the purpose. For example, in one cylinder Lambda 0.95 is set up, on the second – around 1.05, in the exhaust of the current bank approximately 5% of the fuel and exactly the same amount or air leftovers are thrown (for 4 cylinder engine; for 6 cylinder engine – less, because the third cylinder will work with a correct fuel mixture).

In the first case, the wideband probes have to be trimmed very carefully, and the reaction time of the control probe has to be measured; in the second case – the individual adaptations of cylinders have to be performed correctly. Exactly these obstacles (parameters) will affect the test results to the greatest extent.

Solutions, mentioned in both points, could be used because when observing the performance of MSD80 in N43/N53 series engines, the oscillation of the Lambda of the banks is observed, and a short-term disbalance of the fuel mixture of cylinders also.


Stratified charge mode (only MSD80 N43/N53):

DME measures a time during which the fuel thrown in the exhaust during regeneration of the NOx catalytic converter is burned. The change of situation (oxygen – yes/no) is monitored by control probes, additional double control (and at the same time – the test of the sensor itself) is the responsibility of the NOx sensor.


The error messages regarding the performance of CO catalytic converters in Homogeneous mode and Stratified charge are separated. More info here.


Here, a typical error message regarding the lowered performance of CO catalytic converters in Homogeneous mode.

Example of the error message regarding the reduced performance of the CO catalytic converters in Stratified charge:


As already mentioned in other entries (and also follows from the test principle), before blaming the CO catalytic converters itself (if there are error messages regarding their insufficient performance recorded): readapt the engine, make sure, that the injectors are not leaking, that there are no misfires in any of cylinders or any other technical issues (including increased oil consumption), which can cause a false error messages.


If the engine has no obvious problems, a short-term performance reduction of the CO catalytic converters can be caused by a low-quality fuel or driving with a very low load (this is possible only for N43/N53, using Stratified charge in low driving speeds).


Test info of the tests of the CO catalytic converters is very modest. Neither INPA nor ISTA (via EDIABAS) doesn’t reflect the test results.

MSD80 reports the test counters of CO catalytic converters in within OBD Mode 9. Good news: in MSD80 loader 2.023 this OBD 9 mode can be seen here: ../Shift+F1/F9/F2.

These control counters of the performance of CO catalytic converters are not reset under 0 circumstances, it means: they display the complete picture since the “birth” of the vehicle.

Numerator: counter of successful tests;

Denumarator: counter of unsuccessful tests.


As you see, the counter of unsuccessful tests for both banks is identical. Very likely that the reason is that the CO test module is one for both banks – if the test of one bank fails, a fail counter is increased.

The decision for a common test module for both banks would be quite logical, because, for example, the N43 series engine has only one control probe and for several versions – only one CO catalytic converter. Accordingly – it is rational to perform a common test for the whole engine, split by banks if needed. We can assume, that this is a sum of unsuccessful tests of both banks (if the engine has two banks).


My observations indicate, that for cars with mileage with around 100 .. 150.000 km (with regular problems of NOx system and problems with incorrect adaptations in the past) the coefficient counters of CO catalytic converters are at least 70 .. 80%.


Here, another example – a car, which has relatively low mileage (around 150.000), but:

a) this car was excessively driven only in a city with very low speeds (accordingly – its wear of motor hours in true corresponds to significantly larger average mileage as used to);

b) a CCV membrane of the car was broken, its oil consumption was high (more than 1 liter by 1000 km);

c) the NOx sensor of the car was damaged a long time ago (and already the NOx catalytic converters also), which means – the engine works only in Homogenous mode, which only aggravated the problem (in idle in the inlet manifold was a significant thinning, which contributed to sucking of oil from the crankcase).

Although the complete number of the tests is adequate to the mileage, the number of successful tests is very low. The error messages regarding CO catalytic converters were recorded regularly and also during readaptation of the engine – driving even only several tens of km.


As these counters are not deleted, it’s quite hard to use them. To evaluate the actual condition of the CO catalytic converters:

a) write down the counters of unsuccessful and one or both (depending on the configuration of the engine) counters of successful tests;

b) perform a test drive with even driving speed 80 .. 100 km/h (at least 200 .. 300 km);

c) once again write down all counters of tests of CO catalytic converters;

d) calculate the pass/fail coefficient.


Note: MSD80 records the error messages regarding CO catalytic converters earlier than you will not be able to pass TI. Reason for that: during TI the performance of the catalytic converters (CO/HC in the exhaust) is evaluated in “zero loads”. It is clear, that without the load the engine burns a small amount of fuel (only as much as needed to maintain the required RPM), even small remaining efficiency will be enough to burn a small amount of fuel, which gets in the exhaust.


In real conditions, for example, driving with speed 80 .. 100 km/h, with required torque 50 .. 100Nm, the situation is completely different – the catalytic converters have to burn a larger amount of the fuel. So there can be situations when you will be able to pass TI, but the error messages regarding CO catalytic converters will be stored in DME error message memory.


Shortly about consequences, which have to be kept in mind, if the error messages regarding CO catalytic converters are recorded:

a) if the error messages are recorded in Stratified charge, this mode is turned off for some time. When it will be restored, the performance of the CO catalytic converters will be checked repeatedly;

b) if the error messages are recorded in the Homogeneous mode, the torque of the engine is reduced, no enriched fuel mixture in kick-down mode is allowed;

c) if the status of the error messages of CO catalytic converters in Homogeneous mode is active and the power of the engines (accordingly – also the amount of the emissions) is above the norm, established by DME, EML in KOMBI is lighted up;

d) in some conditions Mapped mode (with lowered temperature: 80oC) is enabled.


Counters of CO catalytic converters performance can be seen with EML327 adapter in OBD mode 9.


In the image: ODM mode 9, using Scan Master ELM software:

Unfortunately, EOBD Facile (paid) software don’t display OBD mode 9 data:


Diagnostics example:

N53B30 series engine. After certain time DME writes the error messages regarding the performance of CO catalytic converters both in Stratified charge and Homogeneous mode.

Before blaming the catalytic converters:

a) all possible problems with laking injectors, misfires (ignition systems) were prevented;

b) the engine was re-adapted.


After deleting all adaptations, the error messages regarding CO catalytic converters were not recorded. Here, the table with counters of CO catalytic converters (data of 1st bank):

Data of numerator, denumerator, and mileage: relative, the moment directly after deleting old adaptations indicated as 0.


Counters, when the control of the performance is started:

Counters, when the the error message is recorded for the third time.

As you see in the table, the pass/fail coefficient of CO catalytic converters is very low:

around 22% (2/9) after 9 fail cycles; 25% (3/12) after 12 fail cycles and almost the same: 33% (5/15) before recording the error message (after 15 fail cycles). The average efficiency indicator is around 30%.

As soon as the error message (reduced performance of CO catalytic converters in Stratified charge, Bank 1) was recorded, it was deleted (1st and 2nd time). After 80 km the error message was recorded for a second time and was deleted immediately. After 50 km it was recorded for the third time.

It’s worth to pay attention to as if increased efficiency of CO catalytic converters directly after the error message appeared.

I assume, that it is a peculiarity of the error message management.

Logical action of the owner of the vehicle in case of any defect of the car would be to repair the damaged hub, delete the error messages, if necessary – re-adapt the engine.

In this case – the error messages were deleted without any repair works (because of all systems of the engine work correctly – there is nothing to repair). For the “old” error message not to be recorded directly after its deleting (and it would not confuse the repair specialist), DME gives a small “handicap” to the algorithm of the performance measurements of the CO catalytic converters. Accordingly – if the CO catalytic converters would be replaced, the repeated error message will not be recorded repeatedly (because of the numerator counters would postpone the algorithm from the critical threshold – the number of the positive tests would rise much faster the fail counter).

Instead, with bad performance (not replacing the CO catalytic converters) quickly: after next unsuccessful test – the error message would be recorded again.


This time the most important conclusions would be the following:

a) directly after deleting the adaptations, DME allows bad performance of the CO catalytic converters for a while;

b) obviously, the minimum of the performance of catalytic converters is additionally controlled also after fluctuation of the control probe signals (description will follow), because if the performance of CO catalytic converters is 0, the error messages are recorded immediately (during several tens of km) after deleting the adaptations;

c) in case of deleting the error message of CO catalytic converters, DME gives a small handicap to the system till recording the next error message, it increases the counter of successful tests;

d) in the current case, the performance of the CO catalytic converters is truly bad, because during all 800km tests didn’t indicate good/acceptable efficiency.