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Old 12-23-2016, 01:45 PM   #1
leroge
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Join Date: Nov 2005
Location: Chicago, Illinois
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Cool Upstream O2 Sensors? 2001 E150 XLT 5.4 200K Miles

Getting codes...( Autozone diagnostics )...

P0171 - Fuel system too lean ( cylinder bank 1 )
P0174 - Fuel System too lean ( cylinder bank 2 )
P0153 - HO2S-21 ( Bank 2 sensor 1 ) circuit slow response

Multimetered each upstream O2 sensor....each getting 11+ volts, heating element 3.4 ohms resistance and each producing fluctuating voltages from .2 to .80 after 10 minute idle.

Thoroughly cleaned Mass Air Flow ( MAF ) Sensor with CRC cleaner.

Autozone reference says problem most likely a bad MAF for this vehicle.

Ideas????
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