Readiness Monitors

Readiness monitors show when the vehicle computer has self-tested the emissions control system. This self-test determines if the emissions system is working properly or not. If a number of monitors have not done the check, the “Readiness Result” will be a “Fail”.



PCM won’t go into a ‘Closed Loop’

What is a Closed Loop?
  • Note: Readiness Monitors will not complete without a Closed Loop.
  • Closed Loop is a point where the computer is basing it’s air/fuel mixture calculations on readings from all the sensors.
  • In an ‘Open Loop’ computer is running off a default factory programming neglecting many of the sensors’ inputs.
Sensors are not ready
  • Oxygen sensors in OBDI
    • Many OBDI vehicles with unheated oxygen sensors go to open loop at idle because the O2 sensor cools off and won’t produce a voltage. That’s why OBDII vehicles went to heated oxygen sensors.
      • 📎 Monitors Not Ready | 1987 Chevy R30 7.4L (IATN)
        • Won’t go into a closed loop. Needs a vehicle to be driven to get O2 sensor hot and to enter into a CLOSED LOOP. Also, it might have bad or no  O2 sensor ground, which will prevent a car to enter into a CLOSED LOOP.  With unplugged oxygen sensor (one wire) connectors, it should have 450mV bias.
        • Little bypass method: turn the AC on or, defrost to cycle the AC compressor. It would go into a closed loop and pass no problem.
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