SureTrack Real Fix: Confusing Trouble Code Definitions

SureTrackInsufficient Coolant Temperature for Closed Loop Fuel Control…what does that even mean? Diagnostic trouble code definitions can be confusing, even for an advanced automotive technician. When faced with the two codes that set in today’s Real Fix, some technicians might immediately think, “I will change the thermostat.” or “Those codes don’t go together.” or even, “This doesn’t make any sense, where do I go next?”

Luckily with SureTrack, there is no confusion because the Real Fix below provides a short cut to solving what may seem like unrelated issues.

2000, Lexus ES 300, 3.0


P0125, P1135, Replaced Air Fuel Ratio Sensor (B1-S1)

The customer states the check engine light is on.

Connected a scan tool and found codes: P0125 – Insufficient Coolant Temperature for Closed Loop Fuel Control and P1135 – Air/Fuel Sensor Heater Circuit Malfunction. Performed a visual inspection of air fuel ratio sensor (B1-S1) and the sensor connector, but found no faults. Used a multi-meter to measure the resistance of the air fuel ratio sensor (B1-S1) heater circuit and found the resistance was not within the specified range of 0.8–1.4 ohms at 68 degrees Fahrenheit.

Replaced air fuel ratio sensor (B1-S1), cleared codes, performed a drive cycle and verified the monitor had been completed. The check engine light did not illuminate and no fault codes returned.

SureTrack® is the new groundbreaking expert information feature of ShopKey Pro that brings together a unique combination of intelligence, expertise and real-world parts replacement data, to help automotive shops increase accuracy and efficiency from diagnosis to completed repair.

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