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.
General Information: General Description
When the engine is first started, the fuel control system operates in an open loop method, ignoring the HO2S (Heated Oxygen Sensor) signal and calculating the air/fuel ratio based on inputs from the Engine Coolant Temperature Sensor, the Throttle Position Sensor, and the Mass Air Flow Sensors. The ECM will begin by using the oxygen sensor signal for controlling the fuel delivery (closed loop method) when the following conditions are met:
- The engine has run a minimum amount of time after start up.
- The HO2S has a varying voltage output showing that it is hot enough to operate properly.
- The Engine Coolant Temperature has increased a minimum amount based on the Engine Coolant Temperature at start up.
The ECM monitors the amount of time that passes before the cooling system reaches closed loop operating temperature. If the engine coolant temperature sufficient to allow closed loop operation is not achieved within a predetermined time frame, the ECM sets DTC.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.