Hi Everyone,

Recently I've gotten a check engine light on my ranger. I read the code and it was P0171, System too lean bank 1. The first time I deleted the code and it went away. After a week it came on again and therefore I replaced a cracked air hose (circled in red). The light did not come on for a week until today. Today the code came on again and I don't know where to start. Since it comes on once a week, I assume it's a small air leak or a part that is slowly dying. Does anyone have any advice on this error code? I'm not very skilled with cars but do my best to do everything on my own as much as I can.

The truck is a 1999 4 cylinder and has about 130,000 miles. just changed the oil & oil filter.

Cracked hose.

New hose from Autozone (Continental brand I believe).

Error code.

 

Have you replaced the O2 sensor? Check all the vacuum lines as well.

 

I have not! I'm seeing videos online that reference 'upstream' and 'downstream'. Are you familiar with the distinction and do you know which one I should change?

 

At this point, I would chance both. Up stream is before the Cat. Down is after.

 

O2 sensors are THE ONLY sensors that wear out, 12 years or 100k miles, which ever comes first, is when they should be changed

O2 sensors use a chemical reaction to detect Oxygen in the exhaust, and they simply run out of chemicals, like brakes run out of friction material, or tires run out of tread, lol

After 100k miles or 12 years your MPG will start to go down, unnoticable at first, but over a few years the extra fuel being used could pay for 3 or 4 sets of O2, lol, so changing them SAVES you money