Not ready monitors and hopeful fix - Miata Forumz - Mazda Miata Chat Forums
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NA (1989-1997) NA Miata discussion within. The MX5's first generation, the NA, sold over 400,000 units from 1989 to 1997.

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Old 04-08-2015, 07:14 PM   #1  
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Join Date: Sep 2011
Location: Mt.Peak, Texas
Posts: 190
Default Not ready monitors and hopeful fix

I hope this will help others in the future with not ready monitors,if someone wishes to reword or change it for better understanding you are more than welcome

I have a 1996 miata
I get up and start to go get an inspection and battery is dead. I charge it and without thinking
go to get inspection and I have three not readys O2, EGR, AND CATYLST so that meant doing some driving

Drove and drove and drove some more, even aganist my better judgement I tried three different drive cycles ( I really do not belive there is a true drive cycle ) and still they would not set to ready.
recheck everything have no error codes and nothing that says I have a real problem
A day or so latter recheck and still have the not readys (you can always hope)
Finally , get a P1250 code even though I still do not have a light come on the code is a PRC (pressure regulator solenoid )
Started testing and found a troubleshooting chart and even it is not full proof

Would get air thru ports B & C with no voltage applied and air thru ports A & B with voltage applied. I took it off and hooked to a 12 volt battery and each time I touched the Ground wire the solenoid would click and appear to work . The chart says wire bad or bad ECM if these test are good
Not convinced that wire or ECM was bad, as 12 volts at the connector red/white and 0 on ground green/white
When I connected the PRC to the connector I would not hear a click,only if I applied direct power from the battery would it click as fast as I could activate it

Did an Ohm reading and saw it was above 40 ohms and had seen a video that about 22 is good
purchased a known good PRC and did an ohm reading it read 15 to 20 ohms
Plug it in and test and all seems well
This is a little confusing I could still get 12 volt to red/white and yet with it plugged up and key on I still did not get voltage between the two wires .When I went from the green/white wire to the motor I would get 12 volts. I would think you would get 12 between the two wires that go to the PRC but you don't. I would get 12 volts from the red white to motor as ground and with the PRC plugged in I would get 12 volts from greenwhite wire to motor as ground

Clear the code again and take off within 5 miles all the not readys went ready including the cat
This is the fourth time I have worked on a miata and this is the fourth time the not readys have set without doing a drive cycle. Maybe some need it and some don't as I have done it on two cars twice each and all 4 times no drive cycle was needed
I am convinced if all the parts are workinhg correctly then you do not really need a drive cycle
Something else I would venture is a part can be just bad enough it will not throw a cell or a code but yet bad enough to not work properly.

In my opinion this is what makes the drive cycle theory work. You have a part that is bad ,yet not bad to the point it will give a error code, turn the cel on . After several drive cycle attempts it happens to work and let the monitors set
Here is what I have found as well PRC must work first ,02 sensor must go ready then egr and then cat
O2 has a set time it has to reach temp and is in a time frame of the water heat sensor sends signal to ecu/ecm that it is at temp
Running to much antifreeze or water wetter type products can throw this time frame off
A gentleman named SDB had a problem a few years back and once he fixed his problem he did not really use a drive cycle .At the same time I had a problem and when resolved did not use one either and have not used one since
I try to remember him when I do a error code /not ready repair

Last edited by mytwo; 04-08-2015 at 07:21 PM.
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