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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
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My iat sensor is reading +15 to sometime +30 over ambient

Customer Question

My iat sensor is reading +15 to sometime +30 over ambient temp. Is this normal for 2012 Prius?
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. To clarify, =you are talking about the air temperature sensor that measures the temperature of the air entering the engine, or the temperature sensor that displays ambient temperature outside the car for the instrument panel readout? Please advise. Thanks

Customer: replied 1 year ago.
Engine Intake air temp. Is+15 over the ambient temp displayed fo r ac
Expert:  Toyota Service replied 1 year ago.

That would be considered normal. The two values are not related to each other. The heat of the engine and generators in the engine compartment raises the physical temperature of the tube the air travels in, which heats the air temperature up. The issue is heat saturation, not a problem with the sensor.

Expert:  Toyota Service replied 1 year ago.

Do you have any other questions for me on this request? Thanks

Customer: replied 1 year ago.
The reason I ask is because I've lost about 15-20mpg. The mg feels weak. Cars in closed loop at warm up. And I can't seem to remember but the ltft is+ and stft is- or Vice versa.
Expert:  Toyota Service replied 1 year ago.

I would not be looking at IAT as the issue to cost a 15-20 mpg reduction. I would be looking at the possibility of sticking brake calipers before anything else. Additionally, if this car does not have genuine, factory spark plugs in it ("new" plugs that are not Genuine Toyota can cause a huge drop in MPG), replace the non-factory plugs. Third, ensure you are using the correct weight of motor oil per the service manual. If you are not using what the book requires, you will lose MPG.

Customer: replied 1 year ago.
Lil bit of background. Earlier this year, I got alignment. Pep boys did not do calibration. At the time I didn't know that was part of alignment. The car went to Toyota and they performed calibration but issue was not fixed. On 3rd visit around June I decided to get 30k service. They either didn't do the service and left my car overfilled with 5w-30or they did oil change and overfilled my engine. One hot afternoon, my engine got really loud and I can see heat waves on top of my hood. I looked under hood and can see slight leak or n the t adapter of radiator hose to the resavoir. I clamped it down and car cooled down and quiet on start up. A couple weeks later driving g up a hill, my engine got loud and sounded like the engine is being limited. Went through crap with dealer. I just ended up redoing maintenance. I followed manual. I used 0w-20, coolant exchange on hybrid and gas motors, iridium spark plugs, oil filter, air filter, new battery. Also, while all this degradation in performance, no check light. I also forgot to mention that intermittently, the o2 sensor after cat fails sensor reading test and in while emissions readyness test, heated catalyst test is not applicable. The amount of symptoms and possible problems is overwhelming.
Expert:  Toyota Service replied 1 year ago.

No check engine light indicates a mechanical issue. This car is very sophisticated when it comes to engine management. A sensor or other issue (IAT for example) would cause the Check Engine light to come on. That is why I recommended checking the brake calipers before anything else. Tires with a 'high rolling resistance' will decrease gas mileage, too, but not 15-20 mpg worth. I would be looking for sticking brake issues.

Customer: replied 1 year ago.
Thank you.
Expert:  Toyota Service replied 1 year ago.

Thanks for choosing Just Answer. It was a pleasure to assist you. I trust my input is satisfactory and meets your expectations. A positive rating for my assistance on your request would be greatly appreciated; thanks again and have a great day