Diagnostics Error Code PO170 - BMW z3 1.9 2001 - A Few Pointers...

[Solidsnake0501]

Hi guys, this is my first post and I ultimately joined to try get to the bottom of my diagnostic dilemma... Having now resolved my problem, I just wanted to throw a post together to help others who are no doubt loosing as much sleep as I was.

Anyhow, all the information on the net seems to be a little confusing on the PO170 code and no one really seems to have an answer for it, only that they too have had it.

As we know, BMW do not deal with P codes, so ringing BMW with a P code error is pointless chaps. They will 10 times out of 10 tell you to book it in for a BMW check costing in excess of £102 + VAT.

My vehicle is a BMW z3 1.9l on a 2001 plate. I had the usual symptoms, management light on, kept resetting and came back on usually with in 50 or so miles... This wasn't necesarrily the rule because once it came on after 300 miles and another after 100 so i guess its just down to when it happens.

Things to check, in the order i did are the following:

AIR LEAKS - Air filter, air filter housing, MAF connections, Concertina etc. I changed my air filter as it was ruined. I also found my air filter housing wasn't assembled correctly and the filter not correctly in place.

P0170 will often report FUEL CORRECTION ERROR (Bank 1) MALFUNCTION depending of the tool you use. Bank one refers to PRE-CAT and would suggest the LAMBDA PROBE before the catalytic converter. My 1.9 Z3 has both a pre and post cat sensors. Anyhow, in this instance i replaced the Pre-cat O2 (lambda) sensor with an NTK one, cost about £70. Sadly, where this didn't do any damage, this alone combined with filter work did not rectify my problem. I also afterwards replaced the post cat sensor to no avail!

After 60 miles from Leeds down the M1 my management light came back on again :-( massively annoying as you would expect. A further 20 miles down the motorway and I had a complete loss of power in lane 3 (fast lane) and managed to limp on to the hard shoulder. Know a bit of techie stuff as I do and knowing the MAF was the only thing not replaced, I unplugged it and the car was brought back to life again!

Whilst in limp mode guys, you will often find no power (at all) you will not get the car above 25MPH and dipping the throttle will do nothing, not even register on the rev counter.

In my case, it would appear my Mass Air Flow meter or MAF / MAF SENSOR was the problem. This cost me £170 to replace and its like a new car with power i never knew it had!!!

Where this will not serve as a diagnostics or as a cure to others, it merely details my problems and what I did to fix them. Randomly changing parts is expensive, but start small, preferably with checking for air leaks first.

My car also smelled of fuel on the odd occasion, clearly over fuelling and I was getting approximately 270 miles from a full tank, which is bad!

Anyhow, sorry to bore the experts but i hope people googling the P0170 find this thread and Its helpful to some.. it was a nightmare for me!

Steve