# Engine light on! What is code P0171?

**URL:** <https://community.cartalk.com/t/engine-light-on-what-is-code-p0171/98>\
**Category:** Maintenance/Repairs\
**Created:** [June 1, 2007, 12:55am UTC](https://community.cartalk.com/t/engine-light-on-what-is-code-p0171/98 "2007-06-01T00:55:06Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![cscrna](https://avatars.discourse-cdn.com/v4/letter/c/35a633/32.png) [@cscrna](https://community.cartalk.com/u/cscrna)\
**Post date:** [June 1, 2007, 12:55am UTC](https://community.cartalk.com/t/engine-light-on-what-is-code-p0171/98/1 "2007-06-01T00:55:06Z")

</div>

I have a 1999 Lexus RX 300. The engine light came on and the local auto shop plugged in and came up with this: “P0171 bank 1 system 2 lean” Any ideas? TIA!! Clay

---

<div class="post-metadata">

**Author:** ![me\_art12](https://avatars.discourse-cdn.com/v4/letter/m/839c29/32.png) [@me\_art12](https://community.cartalk.com/u/me_art12)\
**Post date:** [June 1, 2007, 1:41am UTC](https://community.cartalk.com/t/engine-light-on-what-is-code-p0171/98/2 "2007-06-01T01:41:42Z")

</div>

Lean? Could it be the Slim Fast? ++ What is the BASIC cause of a lean engine or a lean cylinder? OK, I looked at the back of the book and got the answer: a lean condition exists when, during combustion, there is too much air, or too little fuel. Too much air could be from an intake manifold vacuum leak near that particular cylinder. Too little fuel could be from the fuel injector not spraying enough fuel.

---

<div class="post-metadata">

**Author:** ![shadetree51](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@shadetree51](https://community.cartalk.com/u/shadetree51)\
**Post date:** [January 26, 2008, 5:50pm UTC](https://community.cartalk.com/t/engine-light-on-what-is-code-p0171/98/3 "2008-01-26T17:50:37Z")

</div>

consider addin sea foam to 8 gallion of gas or less and see if it cleans the system and corrects the problem…

---

<div class="post-metadata">

**Author:** ![lenjack](https://avatars.discourse-cdn.com/v4/letter/l/f475e1/32.png) [@lenjack](https://community.cartalk.com/u/lenjack)\
**Post date:** [January 27, 2008, 12:09am UTC](https://community.cartalk.com/t/engine-light-on-what-is-code-p0171/98/4 "2008-01-27T00:09:05Z")

</div>

I just googled the code and got over 39,000 hits.