Toyota Premio STFT always shows -100%

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Toyota Premio STFT always shows -100%

Postby MasudRM » Sun Dec 03, 2017 10:37 am

Hello guys, 2 weeks ago we serviced 2012 Toyota Premio's Fuel and Intake system including Throttle and also open up the intake manifold and cleaned up. The problem was rough idling. After the service rough idling solved. But after that P0171 started coming on, we even replaced the MAF sensor with a known good one.
The vehicle came back today morning with the MIL on, and guess what it was P0171, with P0401. Also when i checked for data list, the STFT shows negative 100%, and doesn't changes.
Any suggestions...?
Thanks....
MasudRM
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Re: Toyota Premio STFT always shows -100%

Postby Technician » Sun Dec 03, 2017 7:56 pm

First off I'd be inclined to look over the previous work completed to ensure all is in order. The minus 100% STFT tells me that the PCM is subtracting the maximum amount of fuel possible. The P0171 code I think is referring to an air leak, check the hoses, gaskets, vacuum pipes etc. The code P0401 is referring to the EGR insufficient flow I think, but I'd concentrate first of all by going over what has previously been carried out. When you are happy that all previous work is in order, put the scope on the H02 sensor and check operation, also check the operation of the mass air flow sensor.
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Re: Toyota Premio STFT always shows -100%

Postby MasudRM » Tue Dec 12, 2017 7:38 am

Thank You..
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