Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2021 Lexus NX 300h BaseFACTORY OEM SERVICE PROCEDURE
Engine Control System - Diagnostic Codes (2 Of 6)
- SFI System
- DTC P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control [10/2014 - ]
- DTC P0128: Thermostat [10/2014 - ]
- DTC P0136: Oxygen Sensor Circuit (Bank 1 Sensor 2); DTC P0137: Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2); DTC P0138: Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2); DTC P0139: Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 2); DTC P013A: Oxygen Sensor Slow Response - Rich to Lean Bank 1 Sensor 2 [10/2014 - 09/2015]
- DTC P0136: Oxygen Sensor Circuit (Bank 1 Sensor 2); DTC P0137: Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2); DTC P0138: Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2); DTC P0139: Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 2); DTC P013A: Oxygen Sensor Slow Response - Rich to Lean Bank 1 Sensor 2 [09/2015 - 09/2016]
- DTC P0136: Oxygen Sensor Circuit (Bank 1 Sensor 2); DTC P0137: Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2); DTC P0138: Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2); DTC P0139: Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 2); DTC P013A: Oxygen Sensor Slow Response - Rich to Lean Bank 1 Sensor 2 [09/2016 - 05/2019]
- DTC P0136: Oxygen Sensor Circuit (Bank 1 Sensor 2); DTC P0137: Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2); DTC P0138: Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2); DTC P0139: Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 2); DTC P013A: Oxygen Sensor Slow Response - Rich to Lean Bank 1 Sensor 2 [05/2019 - ]
- DTC P014C: A/F Sensor Slow Response - Rich to Lean Bank 1 Sensor 1; DTC P014D: A/F Sensor Slow Response - Lean to Rich Bank 1 Sensor 1; DTC P015A: A/F Sensor Delayed Response - Rich to Lean Bank 1 Sensor 1; DTC P015B: A/F Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1 [10/2014 - 09/2015]
- DTC P014C: A/F Sensor Slow Response - Rich to Lean Bank 1 Sensor 1; DTC P014D: A/F Sensor Slow Response - Lean to Rich Bank 1 Sensor 1; DTC P015A: A/F Sensor Delayed Response - Rich to Lean Bank 1 Sensor 1; DTC P015B: A/F Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1 [09/2015 - 09/2017]
- DTC P014C: A/F Sensor Slow Response - Rich to Lean Bank 1 Sensor 1; DTC P014D: A/F Sensor Slow Response - Lean to Rich Bank 1 Sensor 1; DTC P015A: A/F Sensor Delayed Response - Rich to Lean Bank 1 Sensor 1; DTC P015B: A/F Sensor Delayed Response - Lean to Rich Bank 1 Sensor 1 [09/2017 - ]
- DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1) [10/2014 - ]
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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