Feedback System

ECM calculates base injection pulse width by processing signals from Crankshaft Position Sensor (CKPS) and Mass Airflow Sensor (MAFS), which detect various engine conditions. After receiving signals from each sensor, ECM adds fuel enrichments (preprogrammed into control unit) to base injection width. This provides optimum mixture for a wide variety of operating conditions. Fuel enrichment is always available under the following engine conditions: warm-up, starting, off idle, heavy load and hot engine operation. In addition G20 will also have fuel enrichment when automatic transmission is shifted from Neutral to Drive.

Fuel injection system incorporates mixture ratio feedback. It is designed to maintain a precise mixture ratio so Three-Way Catalyst (TWC) can reduce CO, HC, and NOx emissions. Through use of a zirconia Heated Oxygen Sensor (HO2S) in each exhaust manifold, ECM can decide whether to enrich or reduce air/fuel ratio to precisely control exhaust emissions and engine performance. This function takes place during closed loop operation.

ECM continuously monitors itself to stay within an acceptable emission output range. However, this feedback system can be overridden and will operate in an open loop control condition when one or more of the following conditions exist: vehicle decelerating, high speed or heavy load operation, engine idling, malfunction of HO2S or its circuit, insufficient activation of HO2S at low engine coolant temperature and engine starting. Additionally, on G20, hot engine operation and when all of the following conditions have been met: ignition on, soft closed throttle position switch on, neutral position switch off, engine at idle and vehicle at slow speed will also engage open loop control condition. On J30, HO2S high output voltage will also engage open loop control condition.