# Check engine light with cold weather starts

**URL:** <https://community.cartalk.com/t/check-engine-light-with-cold-weather-starts/83495>\
**Category:** Maintenance/Repairs\
**Created:** [February 2, 2014, 6:27am UTC](https://community.cartalk.com/t/check-engine-light-with-cold-weather-starts/83495 "2014-02-02T06:27:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![S21](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@S21](https://community.cartalk.com/u/S21)\
**Post date:** [February 2, 2014, 6:27am UTC](https://community.cartalk.com/t/check-engine-light-with-cold-weather-starts/83495/1 "2014-02-02T06:27:07Z")

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The check-engine light on my 2006 Toyota Corolla came on a couple of weeks ago after I started the car on a 7-degree F morning. Code was P-0171. Mechanic cleaned the MAF and the light went off. Light stayed off 'til I started the car on another 7-degree F morning. Mechanic said that the MAF didn’t look dirty, and the readings didn’t change after cleaning. No vacuum leaks. O2 sensors responding normally. Any thoughts on what’s going on? I travel a lot in this car, so I don’t want to damage the car by ignoring the check-engine light. Suggestions?

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**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\
**Post date:** [February 2, 2014, 7:37am UTC](https://community.cartalk.com/t/check-engine-light-with-cold-weather-starts/83495/2 "2014-02-02T07:37:47Z")

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@S2

“No vacuum leaks.”

How sure are you?

Did you use an evap/smoke machine to verify this?

Not all vacuum leaks can be heard . . . and not all vacuum leaks can be found with carb cleaner

Anyways, moving on, check this out . . .

[http://www.matrixowners.com/tsb/T-EG051-05.pdf](http://www.matrixowners.com/tsb/T-EG051-05.pdf)

This other bulletin seems to better match your cold weather symptoms

> **[M.I.L.\_ON\_DTC\_P0171,\_AND\_OR\_PO133\_ENGINE\_RUNNING\_LEAN\_IN\_SUBFREEZING\_AMBIENT\_TEMPERATURES\_T-EG045-07.pdf](https://www.toyotaparts.metro-toyota.com/M.I.L._ON_DTC_P0171,_AND_OR_PO133_ENGINE_RUNNING_LEAN_IN_SUBFREEZING_AMBIENT_TEMPERATURES_T-EG045-07.pdf)**
>
> 133.82 KB

By the way, I understand you say you don’t have vacuum leaks, but that second bulletin I posted seems to exactly describe your complaint

Please let us know what finally fixes the car