Fault Code 17538, running lean...

[SyncroS8]

I've got a fault code which keeps popping up.

As above, it's 17538, fuel trim, bank 2, system running too lean.

With the way the system works with faults like this, it has to happen a certain number of times before it bring on the engine lamp on the dash.

By the time it's done this, the corresponding fault code 17536 is also there but it's always the other bank the is first with the fault code.

I've been researching, checking lots and the obvious ones to look at are air leaks, air flow meter, lambda sensors etc.

I've cleaned the air flow meter, checked the readings which register around 20g/s at tickover and 60-80g/s when you boot it. There is a spike when you initially boot off tickover which shows around 160g/s.

Also, readings are similar when driving along. At 2,000rpm it's reading 18g/s and 60g/s when you boot it with the spike as above.

I've checked all over the inlet manifold and found a small plug on the front which was very perished and splitting so I've replaced that.

I've been running it on cheap fuel so this tankful, I've put super unleaded in. No change.

The lambda sensors are all reading similar voltages, the cats are at similar temps etc.

The one thing I've been watching is measuring block 32 which is 02S Adaption Maxims. From what I can see, Bank 2 running leaner than bank 1. See photo below.



I'm still investigating but if one bank is running leaner than the other, that would suggest that the air flow meter is not the problem...

Any ideas?

MG