Ok long story short Polo 2005 9n Twist, 1.2l 3CYL petrol, engine code AZQ (it's the 12 valve).

I've had these engine lights come up every little while for months, I tend to clear the codes and ignore them. P0130, P0172. 

Essentially I plugged it into VCDS tonight, because it's barely doing 30MPG if that, and I'd like to finally sort the issue.

So P0130, Lambda sensor. P0172, engine running too rich. VCDS also kicked out a couple other errors, seemingly low(ish) battery voltage (seems fine to me) and an intermittent error on the AC, about low voltage or short circuit or something.

The thing is I'm not entirely sure where to start diagnosing. If I use the car every other day, the code never appears. If the car sits for pretty much any more than 4-5 days, it comes up. 

I'm thinking replacing the battery might be the way to go, and that the low voltages might be tripping P0130, that trips P0172 in turn, but thats just a theory. The other idea is just start replacing sensors.

It idles fine, runs like a charm, compression tested at last service, bang on 180PSI on each cylinder. 

Any helpful insight?

Thanks

 

PS: Any idea how I could get an MPG display readout in to the car?

Edited 7 May, 201610 yr by MatthewBracey

If at the time the fault occurs, your battery voltage is >12.5 and <15V then thats fine.

As always - your earth bonding must be in good condition and the lambda connections must be clean and dry.

 

At 10 years old the lambda sensor will certainly be slow if not defective.

 

Suggest living it with or start by replacing the lamba.

If you don't want to do that - read the lambda output with your multi meter. If everything is working correctly you will see the value rise and fall at least once a second (once engine is warm).

 

The too rich (max trim reached?) will proabaly dissapear once the lambda issue is fixed but cannot start to be addressed until the lambda is functioning correctly.

 

The is no magic button for this - and trying to diagnose a problem with a 10 year old sacraficial sensor is like passing water in a winward direction.