The exhaust systems of N43/N53 series engines are equipped with 2 or 4 catalytic converters:
1 or 2 CO catalytic converters (1 piece for N43 series engines, 2 pieces for N53 series engines) and
1 or 2 NOx catalytic converters (1 piece for N43 series engines, 2 pieces for N53 series engines).
Image: the exhaust system of N43 series engine (CO catalytic converter)
Image: the exhaust system of N53 series engine (CO catalytic converters and Lambda probes)
The performance of CO catalytic converters is controlled by one or two wide-band Lambda probes (one – for N43 series engines, two – for N53 series engines). More about the control of CO catalytic converters – read here.
MSD80 (for N43/N53) performs the control of CO catalytic converters in two modes: Homogeneous and Stratified charge, each of this modes has separate error messages in error message map.
In case of Homogeneous mixture the CO catalytic converters have larger “workload”, so in normal situation (when CO catalytic converter’s performance decreases because of deterioration) the error message regarding decreased performance of them will be receded in Homogeneous mixture mode at first. If the performance of CO catalytic converter is very, very weak (close to no performance), MSD80 records error message also in Stratified charge mode.
If the error messages regarding decreased (insufficient) performance of CO catalytic converter are recorded in Homogeneous mixture mode:
a) error message codes: 29F4; 29F5 (1st and 2nd bank accordingly);
b) MSD80 performs regular peed of enriched fuel mixture (Lambda around 0,97) to catalytic converters with purpose to “heat” them up – to increase the temperature (tries to restore performance of CO catalytic converters);
c) MSD80 turns off the Stratified charge for upper region of this range (Stratified charge is left only for idle and low load conditions, for example, driving with speed max 50 .. 60 km/h, or, if the performance of CO catalytic converters is very low – Stratified charge is turned off completely).
If the error messages regarding insufficient performance of CO catalytic converters are recorder in Stratified charge mode:
a) error codes: 2A26; 2A27 (1st and 2nd bank accordingly);
b) MSD80 completely turns off the Stratified charge;
c) the engine temperature is decreased from Normal/Eco mode (100 .. 110 oC) to 75 .. 80 oC.
In case, when Stratified charge is turned off completely, the problems, which are typical in case of damaged NOx system – uneven running of engine, error messages regarding trim, misfire etc. are possible (and in longer run – are inevitable), because the creation of long-term trims is disrupted.
Note: it is interesting, that the N43 series engine has two different error messages regarding performance of CO catalytic converter (for each of banks), but the catalytic converter is only one. Usually as first are recorded error messages regarding CO catalytic converter of 2nd bank – the Lambda control probe is placed in exhaust pipe of second bank (before Y-type connection).
If the Stratified charge is completely turned of because of insufficient performance of CO catalytic converter:
a) if the error messages recorded are 29F4 and/or 29F5, error messages regarding total loss of performance of CO catalytic converter (and, accordingly, error messages 2A26; 2A27) can also not be present (even if the CO catalytic converters have lost all work possibility), because the engine has not worked in Stratified charge/hasn’t worked in Stratified charge, and there are no conditions to check performance of CO catalytic converter in this engine mode;
b) the error message relating aging of NOx catalytic converter also can not be present (error message code: 30E9) in case of insufficient performance of NOx catalytic converter, because the performance of NOx catalytic converter is not controlled in Homogeneous mode conditions.
To approximately evaluate the performance of CO catalytic converter:
1. delete long-term trims of MSD80, delete error message memory.
Create new long-term trims. If in the process of creating new long-term trims error messages 2A26 and 2A27 are observed – the performance of CO catalytic converters is very low. Unlikely the “heating” and/or some chemical additives will help.
2. if after a while the error messages 19F4 and 29F5 appear – check, if the long-term trims are been created correctly.
If the long-term trims are performed correctly, you can measure CO/CH.
When the engine is heated up, turn on the Homogeneous mode with Lambda 1,00 (INPA: ../F9/F1, press F4). If the measurements (with reserve) fit in TI norms, can be assumed, that there, however, are/were some problems with creating of individual long-term trims.
In this case: check the coding of injectors (the problem described here), eliminate all other error messages and also their causes (especially everything that concerns NOx system), fully delete all long-term trims of 2-nd group, very carefully perform new long-term trims (how – read here and here).
Note: don’t forget to turn off the forced mode! How to do it safely: turn on the Stratified charge (..F9/F1, press F3), make sure, that the engine works in Stratified charge (it it’s allowed), then press F5, to exit the management of forced engine mode.
In case of reduced performance of CO catalytic converter also the desulphuring of NOx catalytic converter can be disturbed, accordingly – after some period of time also error message 30EA will appear, even if you regularly drive with speed above 110 .. 115 km/h and there are all conditions for NOx catalytic converter to desulphurise.
The idea to “cheat” the control probe of CO catalytic converter was very tempting, especially keeping in mind, that if N43/N53 series engines perform in Stratified charge mode, the amount of emissions is tiny and easy fits in TI norms.
Unfortunately the attempt to modify the exhaust system with the goal the decrease the speed of airflow to control probe, failed. If the reduction of air inflow was too little, MSD80 detected insufficient performance of CO catalytic converter, if the air inflow was too high – also the signal of control probe is detected are incorrect (because of growing group delay). MSD80 immediately detected slow response of control probe, tried to additionally heat/cool down the control probe (perform the self-tests) in Homegeneous mode (which, of course, didn’t succeed – the signal of probe is recognized as faulty).