This is not the most complicated case in my experience. But – I decided to share my experience because, at this time, the complexity of the problem hides somewhere else. There is a minimal amount of data. Two images. Only the list of error messages of all blocks and the Fuel mixture menu. Is it enough? Let’s check the situation together!
Car: N53 series engine. A short story from the owner: the engine regularly works on 5 (of 6) cylinders, shivers. The service has replaced the following parts: ignition coils, spark plugs, and fuel pump. Nothing helped.
Here is the information which was sent to me:
What do we see in these images?
Misfires in all cylinders of the second bank. And additionally:
2A2C fuel mixture control 2
2C7E Lambda probe behind the catalytic converter, trimming control
2C3C Lambda probe in front of the catalytic converter 2, not plugged
It is clear that there are fuel mixture problems in the 2nd bank. In addition, the error messages are regarding both (wideband ann control) probes of the 2nd bank.
Let’s see the fuel mixture data – incorrect values I marked with red:
Lambda 16? Could it be?
Lambda 16 means that there is clean air in the exhaust. Could all cylinders of the 2nd bank have been switched off?
No, this is not a plausible scenario. There are several reasons:
a) if all three cylinders were switched off, it would not be possible to drive a car (if it is equipped with an automatic gearbox);
b) a strong argument: STFT (Integrator) is +30%, which means – DME works in Closed loop mode. If at least one cylinder is switched off, the appropriate bank is switched to the Open loop mode; Integrator is 0.
So – all injectors are managed, but the Lambda probe indicates 16? There is no slightest doubt – the wideband probe is damaged. This is the most popular defect of these LSU 4.9 probes (reporting a significantly leaner fuel mixture).
Note: the error message 2C3C does not actually corresponds to the truth. If the probe is not connected; the current of its Pump cell is not flowing. DME receives information that Lambda is 1.00 (regardless of the actual composition of the exhaust gases). Instead, 2C7E is the consequence of the existing defect of the wideband probe. It is clear that it will not be possible to trim the defective probe. Here – one additional note: as the attributes of the error message mention the control probe, typically – mechanics replace exactly that one. But, actually, the meaning of the error message is the following – DME did not manage to trim the WIDEBAND (in front of the CO converter) probe using a control probe! In this case, the problem can hide both in the wideband probe and in the excess air suction. The description of the error message is misleading!
Conclusion. I have no objections regarding the replacement of the spark plugs. They have to be replaced regularly. The ignition coils for these engines are not eternal too. But, if there is a problem exactly with the cylinders of one of the banks (in this case – the 2nd bank). The service should be able to logically conclude that the problem is precisely in this bank! The fuel pump, instead, is one for all cylinders. The defect of the fuel pump can not affect only one bank.
