Circuit Description

When the air fuel ratio feedback is stable after engine warming up, the fuel trim is considerably in error on the RICH or LEAN side. Possible causes are:

• Air intake (hose area)
• Fuel line pressure
• Injector blockage
• Heated oxygen sensor malfunction
• Mass Air Flow (MAF) meter
• Engine Coolant Temperature (ECT) sensor

Fig 1: Code P0171 & P0172 Flow Chart (1 Of 3) Fuel Trim

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Fig 2: Code P0171 & P0172 Flow Chart (2 Of 3) Fuel Trim

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Fig 3: Code P0171 & P0172 Flow Chart (3 Of 3) Fuel Trim

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002