I've just had my engine warning light come on on my last drive. Plugged in the ODB2 reader to see that it's the P0171 error code, so it thinks the system is too lean.
I haven't had a chance to poke under the engine bay due to the rain, so I thought I'd plug my laptop in and use FreeSSM to see what's happening.

On the initial idle from cold the A/F learning was around 14%, so pretty high. It did reduce a bit when the engine warmed up. I decided to reset the ECU, so clearing the error code too. When running the engine again and going for a short drive the A/F learning sat around 0-0.8%, so more sensible. But have I just effectively got the ECU to recalibrate itself around a fault with the engine? Is there anything else I could analyse from FreeSSM parameters to see if there's any tell-tale signs of problems?

 

It will probably be one of the lambda sensors in the exhaust.

 

 

I found this split in my inlet hose. While it would mostly be pressed against the next tube, I do wonder whether it was letting through a little bit of air. I've glued it up for now, and hopefully will improve things. The warning light hasn't come back on and the engine seems to be running OK; though I haven't had the chance to give it some welly.

 

Can't see that being your problem. Have you any exhaust leaks.

 

I haven't noticed any exhaust leaks, at least nothing sounds leaky exhaust-wise. It's not the easiest exhaust system to poke around on though.
The other possibility is the O2/air-fuel sensor is a bit ropey. It's generating a plausible signal, so not completely broken, but I wonder if it's just a bit past it and not quite reacting with a good enough signal.