OBD II code P0171 - Toyota Nation Forum : Toyota Car and Truck Forums

raycwang · 01-10-2005, 11:20 AM

I have a '99 4 runner SR5 4WD with the check engine light on, the OBD II code is P0171 engine too lean. I cleaned the injector and changed the O2 sensor in front of the catalytic converter, but the light and code come back again. Any ideas whats wrong? No problem driving or starting at all.

***humanoid*** · 01-10-2005, 11:58 AM

Check your mass air flow sensor that's connected to the intake tube. Take it out and clean it with electrical contact cleaner. Spray it down, wait for it to dry and slap it back on. Also you may also want to reset the ECU. You can do that by opening the fuse box and taking out the little 15 amp EFI fuse for a few minutes while the engine is off and then replacing it. That should clear your CEL. Below is a link to how to properly clean your MAF sensor.

http://www.4x4wire.com/toyota/mainte...ncep5.html#maf

hpyman123 · 01-10-2005, 10:05 PM

Check the intake tube for breaks and that it is sealed. Those tubes have a tendancy to crack and break in the areas where it flexes. Take it off and inpect thoroughly sometimes they have cracks in between the ribs.

raycwang · 01-17-2005, 05:02 PM

I cleaned the MAF sensor last weekend, so far the ckeck engine light has not come on yet, it seems did the trick, Thanks!

Smoke · 01-17-2005, 08:06 PM

Are you using the K&N air filter?