What causes catalyst monitor not ready?

What causes catalyst monitor not ready?

If the oxygen sensor and catalyst monitors are also not ready, the culprit is most likely a weak battery. If your battery is more than four years old, replace it and re-run the Drive Cycle. Even though your car may start just fine, the PCM is hypersensitive to the slightest glitch in the battery.

How do I clear my o2 sensor monitor?


  1. Start engine cold from sitting overnight and allow the engine to idle normally for 2 minutes.
  2. Drive the car around normally for 10-15 minutes to fully warm up the engine.
  3. Accelerate to 20-30 MPH and maintain steady speed for 3 1/2 minutes.
  4. Accelerate to 40-50 MPH and maintain a steady speed for 15 minutes.

How long does it take for O2 sensor to reset?

Turn the ignition to the on position but do not turn on the engine (it will not start anyway). After five minutes, reinsert the fuse. The lamp of the check engine will blink and then turn off, indicating that your ECU has been restored.

How long does it take to complete a drive cycle?

Always refer to your vehicle service manual or a professional mechanic who has access to the exact drive cycle instructions — and follow them to ensure accuracy. In most cases, a correct drive cycle will take no longer than 15 minutes to complete.

Can you pass emissions with catalyst not ready?

Depending how old your vehicle is, the catalyst monitor might be allowed to remain incomplete and the vehicle still pass the smog inspection. Currently 1999 and older gasoline powered vehicle’s are allowed one incomplete monitor.

Should I disconnect battery before changing O2 sensor?

No, there is no need to disconnect the battery when replacing O2 sensors. Unplug the wire at the connector and remove O2 sensor.

Where are the oxygen sensors on a BMW E46?

In the BMW E46 6-cylinder engine, a pair of oxygen sensors is installed in the exhaust manifolds just ahead of the catalytic converters and another pair is in the pipes just after the converters. Once the engine reaches operating temperature, output from the precatalyst pair of sensors settles into a steady wave pattern between 0 and 1 volt.

Why are oxygen and catalyst sensors not ready?

Oxygen and catalyst sensors… Just had the charcoal canister replaced, check engine light is now off, but oxygen and catalyst sensors are showing as ‘not ready’ and vehicle will not pass emissions. Car has been driven over 200 miles and sensors still show ‘not ready’ Battery was replaced last summer.

Do you need to test the O2 sensor?

Thank you for your time. Depending on a manufacturers strategy for confirming if the evaporative system purge valve can draw vapors, the O2 sensor system might need to be tested by the onboard computer first. A lot of vehicles watch for a shift in the fuel trim when the purge valve is turned on and off confirming that flow took place.

Why are two monitors not ready for OBDII?

For many people that can be the amount of driving they do an entire year. I usually expect to see a 1999 pass with two monitors not ready as the cut-point to one monitor incomplete is 2000. Even so, the progressive nature of OBDII causes certain tests to be blocked from running until the correct conditions are achieved.