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Toyota Repair/Cooling Fan

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QUESTION: My cooling fan does not come on.  It will turn on immediately when I turn on the AC, but doesn't turn on when the engine is running without the AC.  I've change the thermal sensor so far, what should I do next?  

In addition to that I failed emissions this morning, high HC and CO.  I found afterwards that the O2 sensor on the exhaust manifold was completely unplugged.  Is this likely the only reason why or should I look for other issues.  This car only has 47k original miles and runs perfect.  It passed with flying colors last time with no repairs since then.

ANSWER: Hello, I need to know which model and year Toyota you have. First reconnect the sensor, disconnect the battery for a few seconds, this should clear the code, then drive it and see if the light turns back on.

---------- FOLLOW-UP ----------

QUESTION: Apologies, I thought I had given that info.  1991 Toyota Tercel with automatic.

ANSWER: No problem, by "thermal sensor" do you mean the sensor at the bottom of the radiator? When you disconnect the connector and turn the key on does it run all the time?

---------- FOLLOW-UP ----------

QUESTION: I've resolved the cooling fan issue.  Due to the fact that this has sat for so many years without being driven the contacts inside the motor weren't making good contact.  I disassembled the fan motor, cleaned everything, and touched things up with a bit of sandpaper, and it works perfectly now.  

What do you think about my emissions question?

"In addition to that I failed emissions this morning, high HC and CO.  I found afterwards that the O2 sensor on the exhaust manifold was completely unplugged.  Is this likely the only reason why or should I look for other issues.  This car only has 47k original miles and runs perfect.  It passed with flying colors last time with no repairs since then."

I get one free retest but wondered if there was anything else that I should look at before heading back to the testing station now that I plugged in the sensor?  Thanks for your help.

Answer
Reconnect the sensor, clear the code and drive it to see if a check engine light turns on, if it runs and idles smooth and the light stays off chances are good that it will pass, you may also consider getting a can of fuel additive that can bring the emissions down, these are available at most auto parts stores.

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I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.

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