Feedback System

PCM calculates base injection pulse width by processing signals from CMP sensor and mass airflow sensor. After receiving signals from sensors detecting engine conditions, PCM adds fuel enrichment (preprogrammed into control unit) to base injection width to obtain optimum fuel mixture for all operating conditions. Fuel enrichment is always available during warm-up, starting, off idle, heavy load and when engine temperature is great.

Fuel injection system incorporates mixture ratio feedback. It is designed to maintain a precise mixture ratio. Through input signals from heated oxygen sensor, PCM can adjust air/fuel ratio to optimally control exhaust emissions and engine performance. This function takes place during closed loop operation. PCM continuously monitors itself to stay within an acceptable emissions output range. However, this feedback system can be overridden and will operate in open loop when one or more of the following conditions exist:

• Starting.
• Engine and/or oxygen sensor cold.
• Driving at high speeds or under heavy load.
• Oxygen sensor monitors a too rich condition for over 10 seconds.
• Fuel shutoff solenoid is activated.
• Vehicle is decelerating.
• EGR temperature sensor is malfunctioning.