1999 BMW 318



October, 27, 2009 AT 5:51 AM

Computer problem
1999 BMW 318 4 cyl Two Wheel Drive Manual 87000 miles

I have had the computer scanned. It tells me there is an air leak on the fuel system. Have checked from the air filter to engine cannot find fault can you help, please.
The code readout read;
code 171 check fuel supply system (EUIII code: P0170)

thank you.

tony (london, U.K)


3 Answers


Dr Loot

October, 28, 2009 AT 12:19 AM

According to my OBDII manual, a code 171 indicates that the system is running lean. This is not necessarily from an air leak. It could be a faulty mass air flow meter, or could be something as simple as plugged injectors. My first step would be to put some injector cleaner in the fuel tank. My personal choice would be BG44K, although it is not carried in many parts stores. After that, I'd try to find a friend with the same car and temporarily swap MAF sensors with him to see if that cures the problem and moves it to his car. Finally, you can check for vacuum leaks by spraying starting fluid around your hoses and listening for an engine rpm change. The boot from the throttle body to the mass air flow sensor is the most likely culprit. Inspect it carefully.

Good Luck

Dr. Loot's Assistant



November, 3, 2009 AT 10:11 AM

Thank you for your reply.
I have changed the mass airflow meter.
Can you tell if the engine light that is on can be reset without a diagnostics computer.

Thank you


Dr. Hagerty

November, 3, 2009 AT 11:23 PM

No, it cannot. It will take a scanning device to reset the light. Also check the tank vent valve. Go to Realoem. Com for the exploded view of the valve and it is located on the intake manifold. Part # 11-15-7-501-567

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