My 03 S has been throwing a P0171 for the last few weeks. It has shown up twice while cruising on the highway and three or four times immediately after I start the car. I can't clear the code with my scanner which is odd. It self clears after a few days though. The car is running fine with no indication of what is causing it. I have sprayed starter fluid around all the intake connections looking for a vacuum leak with no luck. Any ideas on what I should be looking for as to what is causing the code to appear?

 

whats that code mean?

 

Lean on Bank one.

It would make more sense if it only came on when driving on the highway. Like I said though last few times it's comes on right when I start the car. There's no way it can decide that quickly that the system is lean. Especially during cold start up.

 

why not? the computer is making hundreds if not more, calculations per second. It could be a pending code, I get codes for over boost or leaking air sitting at stop lights sometimes. the ECU will turn off CEL lights after 5 cycles of no code seen in the engine.

maybe some injectors are clogged? or lines? you run high octane gas? injector cleaner? Mini may have a specific meaning to that code, vs the "generic" meaning seen on many code readers. there could be other codes behind it as well. has mini checked it for you?

 

It isn't using the O2 sensors at cold start up so there is no way for it to know it is lean yet. They are not warm enough to provide any type of accurate reading so they are ignored.

I don't think it is a fuel supply problem. It never happens under aggressive throttle use. Only under light load or at start up.

I would never bring the car to Mini. Besides the incredibly inflated pricing the few interactions I've had have shown me if it's not a normal problem they have no idea what is going on. That really goes for 90% of the mechanics out there.

 

oh. sorry to hear about your bad interactions with mini. guess im lucky, here in orlando, they've done basically all my tuning and upgrades and have been very helpful and knowledgeable. they often go out of their way to fix little stuff on my ride too.

what sensors ARE used in measuring "bank 1"? or, better yet, where IS bank 1?

 

I have run into this code twice you would never expect to be the Mass air flow sensor but both times I replaced this sensor and it cured the problem code

 

Here's a list of items to get you going...

P0171: Fuel Trim; Bank 1: System Too Lean

Possible Causes
Mass Air Flow Sensor defective
Intake System Leak(s)

Possible Solutions
Check Mass Air Flow Sensor
Check Fuel Pressure Regulation
Check Fuel Pump
Check Injectors
Check Intake System for Leaks
Check Exhaust System for Leaks
Check Secondary Air System for Leaks
Check Vacuum Pipes for Leaks

I'd start by checking for leaks in the intake and vacuum system. Once you've done that, check the fuel pressure coming from the fuel pump, the fuel pressure regulator (FPR). A faulty Mass Airflow Sensor can cause this code... then go down the list.

My 1.8T New Beetle has had this code on/off the last few months. It's a general "lean" code which points to many things not functioning correctly but not so severe that would cause the CEL to flash, which is a warning of possible damage in VW system of warning. The idle is stable, MPG is consistent. I've just replaced semi-dead PCV and related hoses that are the primary cause of this code. Didn't work. Next up is tearing into the intake side and check for air leaks. This a PITA as it has some 10+ rubber hoses between the Mass Airflow Sensor and the turbo that work together to control the vacuum system, the waste-gate, diverts and recirculates turbo pressure. And if that doesn't work, then I go after are fuel pressure regulator, injectors, Oxygen sensors.

You're right to be skeptical about the dealer. If the technician and SA are honest, they would diagnose each and every item and narrow down the problem. That would mean: fuel pressure test, injector test, reading of oxygen sensors fore & aft the CAT, smoke test for vacuum leak, MAF test, etc. However, a lazy tech will just start with the most expensive items first - MAF, oxygen sensors, injectors - before he even try to check for a simple thing like an intake leak.

Good luck to you... and let us know once you've found the problem.