Auto Repair 2000 Toyota Tacoma Dtc P0125 Insufficient Coolant Temp For Closed Loop Fuel Control

Auto Repair 2000 Toyota Tacoma Dtc P0125 Insufficient Coolant Temp For Closed Loop Fuel Control

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CIRCUIT DESCRIPTION To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way cata- lytic converter is used, but for the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio. The A/F sensor has the characteristic that provides output voltage* approximately proportional to the existing air-fuel ratio. The A/F sensor output voltage* is used to provide feedback for the ECM to control the air-fuel ratio. By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air-fuel ratio and control the proper injection time immediately.

If the A/F sensor is malfunctioning, ECM is unable to per- form accurate air-fuel ratio control. The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temp. of the exhaust gas is low), current flows to the heater to heat the sensor for accurate oxygen concentration detection. *: The voltage value changes at the inside of the ECM only. INSPECTION PROCEDURE HINT: S If the vehicle run out of fuel, the air-fuel ratio is LEAN and DTC P0125 will be recorded. The MIL then comes on. Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction. S