Code P0170

Flatulentoldgoat

So I had this on a Nissan Note 2011 and I cleared the code. Couple of months later, it's back. Clearly there's an issue that needs sorted although the car drives and behaves as it should. Any suggestions or advice on fixing it. Or just leave it? Will it be mega £££ warranting a full engine strip down (well you know what some garages are like...)

facade

P0170 means the fuel trim has hit the end stop. Probably the pre-cat oxygen sensor is faulty, and it is trying to run over-rich, I'd expect a code indicating a mixture error before long.

Is it using more fuel?

It could indicate other faults like low or high fuel pressure, dirty aircleaner or a faulty airflow sensor.

Flatulentoldgoat

facade said:

P0170 means the fuel trim has hit the end stop. Probably the pre-cat oxygen sensor is faulty, and it is trying to run over-rich, I'd expect a code indicating a mixture error before long.

Is it using more fuel?

It could indicate other faults like low or high fuel pressure, dirty aircleaner or a faulty airflow sensor.

I can't discern it using more fuel. I already get a very healthy MPG (60 mpg on long runs) though I've always noticed a sort of turbo-lag going 3>4 gear. Either way, worth getting on with life or taking it over to a garage?

This has been going on for over a year mind you. Probably longer had I not picked up an OBD

facade

It could be an over lean mixture, did it pass emissions at MOT with it like that? 

Check the air cleaner, and look for split/broken hoses, then if it isn't giving any trouble and it MOTs it is up to you whether to spend on getting it looked at.   I'd mess about with it myself, not having a temperature gauge worries me with mixture faults.

Flatulentoldgoat

Never had a problem with anything emissions related on an MOT. If it were bad injectors, or something more expensive would there be any tell-tell signs?

Goudy

P0170 is, as already stated a fuel correction code.

The engines PCM has got the the end of what is possible when trying to trim the fuel to balance with the amount of air entering the engine.

Basically, it thinks it has or has more air entering the engine than it can add fuel for.

Most common actual fault for this is air/vacuum leaks, so the engine is drawing in unmetered air via a leak somewhere, like a split or cracked hose. (engine breathers and brake servo hoses are common)

There could also be some "perceived" faults, like a misreading of the air entering the engine, say MAF or MAP faults or misreadings of air content in combustion from the pre car O2 sensor because or an O2 fault or a small hole in the exhaust. (if it's driving with a bit of turbo lag, that might be favourite)

Your basic diagnostic reader has pulled the code, but you really need to log what these sensor above are doing (and know what they should be doing) to try and pinpoint where the fault actually is.

Flatulentoldgoat

Very helpful, though I'm still not sure how 'serious' the issue is and whether it warrants a garage inspection. I'll have a visual though and if there's nothing obvious than perhaps I'll rethink.

Goudy

Check the exhaust, particularly up stream close to the flexi pipe.

Then check all the hoses carefully, the vacuum and breather hoses around the throttle body.

I'm not over familiar with Nissans though I guess I might soon be as I now have a Renault/Nissan alliance engine, but I believe the EVAP purge valve is a little prone to failing so can draw unmetered air in via that, though I would expect a related code. (P0443 or P0444)

Flight3287462

We have a the newer model Note 1.2 DGiS and it has not enjoyed lockdown (lack of use) throwing a few codes which it went in to the garage for they could find no faults and in the end clearing the codes and a bit of Italian tuning seems to have cured the problem.  Try the Nissan Note Owners forum if your still worried.

Flatulentoldgoat

So on the intake pipe, it's a plastic job which splits/separates to form both halves. I found right at the bottom where it connects down on the connecting pipe to the MAF there was an ever-so-slight split. So I pulled the top half off the pipe and re-snapped it back together starting from the MAF end where it was lose and worked my way back. Seems to fit snuggly as it should now. I'll see what happens, I'd be surprised if this fixes it as it seemed very minor.

Goudy

If it was able to pull in air between the MAF and the engine, that could very well be the problem.