What speed is necessary for the PCM to switch to Closed-Loop mode?

What speed is necessary for the PCM to switch to Closed-Loop mode?

• A. Low RPM
• B. Idle RPM
• C. High RPM
• D. Mid-Range RPM

Answer: (C)

Closed-loop fuel control relies on sensor feedback to keep the air-fuel ratio near the target. The PCM switches to this mode once the engine is warmed up and the sensor readings are reliable, which happens at higher engine speeds. At higher RPM, the oxygen sensor responds quickly and the exhaust gas composition is stable enough for accurate feedback, allowing the PCM to adjust fuel precisely in real time. At idle or low RPM, signals can be slow or noisy, especially before warm-up, so the PCM typically stays in open-loop during those conditions. Therefore, higher RPM is the condition that enables switching to closed-loop.

Closed-loop fuel control relies on sensor feedback to keep the air-fuel ratio near the target. The PCM switches to this mode once the engine is warmed up and the sensor readings are reliable, which happens at higher engine speeds. At higher RPM, the oxygen sensor responds quickly and the exhaust gas composition is stable enough for accurate feedback, allowing the PCM to adjust fuel precisely in real time. At idle or low RPM, signals can be slow or noisy, especially before warm-up, so the PCM typically stays in open-loop during those conditions. Therefore, higher RPM is the condition that enables switching to closed-loop.