What is the lowest engine temperature at which the PCM will not switch to open-loop?

What is the lowest engine temperature at which the PCM will not switch to open-loop?

• A. Engine Coolant Temperature
• B. Cold Start
• C. Minimum Temperature
• D. Fuel Pressure

Answer: (C)

Fueling strategy in the PCM changes with temperature. When the engine is cold, the PCM runs in open-loop, using predefined fuel maps and not relying on feedback from the O2 sensors. As the engine warms and reaches a defined minimum temperature, the PCM switches to closed-loop, using the O2 sensor feedback to trim the air-fuel ratio. The lowest temperature at which it will not stay in open-loop (i.e., the point where closed-loop can begin) is this minimum temperature. That’s why the right term is minimum temperature. Engine coolant temperature describes the actual reading, cold start is a condition, and fuel pressure isn’t the temperature threshold used for this decision.

Fueling strategy in the PCM changes with temperature. When the engine is cold, the PCM runs in open-loop, using predefined fuel maps and not relying on feedback from the O2 sensors. As the engine warms and reaches a defined minimum temperature, the PCM switches to closed-loop, using the O2 sensor feedback to trim the air-fuel ratio. The lowest temperature at which it will not stay in open-loop (i.e., the point where closed-loop can begin) is this minimum temperature. That’s why the right term is minimum temperature. Engine coolant temperature describes the actual reading, cold start is a condition, and fuel pressure isn’t the temperature threshold used for this decision.