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Check engine light - 12/20/2005 7:12:23 AM

VT STANG

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Joined: 12/20/2005
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Hi, I'm new here and have a problem with a 95 Millenia. The check engine light came on, I checked it and got 3 codes. P0725, P1195, and P1000. I'm not really sure what they mean. If someone could point me in a direction I would apprieciate it. thanks in advance

Jason

Post #: 1

RE: Check engine light - 12/20/2005 8:53:19 PM

babyhuey

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Joined: 7/28/2005
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Posted this in your general tech thread but will put here as well.

The P1000 means that not all of the on-board system tests have been run or completed. Not a worry on that as a 95 Millenia is close to impossible to run the catalyst monitor.
The P0725 indicates that the Transmission Control Module is not getting a engine speed or tachometer signal from the Engine Computer. Does the tach on the dash work?
Assume you have a Millenia with the 2.5l engine as the 1195 code does not apply to the 2.3l engine operating system. A P1195 says the the barometric pressure signal was not within range. The engine computer does a one time check of baro pressure thru the boost sensor when key is cycled to run but before start-up. If the signal voltage is out of normal range then will set the code. Have replaced a dozen or so sensors for this but either check or have checked out first as the sensor is around $260.00 and is kind to spendy to be guessing at.

(in reply to VT STANG)

Post #: 2

RE: Check engine light - 12/20/2005 10:06:41 PM

keninn

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Joined: 9/2/2005
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there is a 95 s here with the 1000 code, and he has run it thru a full tank of gas, and the code stays. this car has 220k on it, and is kinda ragged out. is it possible that the ecu has gone open loop? the info is kinda vague, saying that the onboard tests have not been run. since the car has gone like 300 miles, i would think that the systems tests have plenty of time to be completed. i know on the mitsu, if o2 trim stopped cycling and stuck on 100, it means the ecu has gone open loop.

(in reply to babyhuey)

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RE: Check engine light - 12/20/2005 11:39:36 PM

babyhuey

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keninn, the 95 mill is barely OBD2 compatible and was Mazda's first attempt at making them so along with the 95 Protege. Have seen a 95 go for 10k miles without running all of the monitor systems. There are a series of drive modes that you can put them thru to pass the monitors but they barely work as well. Do you know which monitor has not passed?

(in reply to keninn)

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RE: Check engine light - 12/22/2005 9:31:11 AM

keninn

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here is his post with the solution:

I spent 1 month troubleshooting a P1000 troublecode - System Readiness Tests Not Complete (CEL does not light up for this code). Normally, P1000 code occurs when computer error codes are reset. The P1000 code signifies computer is running the car from factory fuel trim settings (open loop mode) until the System Readiness Tests are completed. Once the System Readiness Tests are completed, if nothing is wrong the computer will go into closed loop mode and operate the fuel trim setting based off of the O2 sensor readings. My car was stuck in P1000 mode for ever. I just recently found out why. Someone had miswired the bank 2 rear O2 sensor, which inturn damaged the input to the Engine Control Module (computer).

this makes diagnostic sense. system stays in open loop default mode, until all the sensors come on board. if 1 or more sensors are out of tolerance, it stays in open loop. i think on later obd 2 cars, ecu has the ability to override certain inputs, and use default inputs, but not all inputs. this would be ce lite on, car can still be driven. when certain other inputs are out of tolerance, probably those which affect emissions, ecu then makes ce lite flash. just a wag. i bet on the 95 car, if it is operating fine, then sensor input goes bad, it will lite the ce and throw a code for each bad one, AS LONG AS IT INITIALLY COMPLETED THAT READINESS TEST. then, when it is shut off and restarted, it stays open loop, and throws the 1000 code, but probably also keeps the other codes in memory. if the ecu is reset, all codes erased, when it is started, it stays open loop, throws the 1000 code, but now you have LOST the other codes, so you dont know why. another wag. waddya think?

(in reply to babyhuey)

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RE: Check engine light - 12/22/2005 3:52:43 PM

babyhuey

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Well, yes and no. Right in that open loop means that PCM is controling fuel delivery and amount based on preset operating parameters and is not responding to oxygen sensor signal as it is not accurate when cold. Closed loop would then be when the oxygen sensor has warmed up fully and giving accurate reading of exhaust oxygen concentrations and PCM can use this to increase or decrease fuel amount to keep it as close to stoiciometric of 14.7:1 as possible.

P1000 does not mean that fuel control is in open loop. P1000 only means that not all of the on-board system readiness test have either passed or even ran for that matter.If test monitor is ran and failed it will either turn on the CE light or set a pending code with no CE untill test is ran again and either passes or fails the second time. These monitors include oxygen sensor monitor (including heater monitor), evaporative system monitor, EGR monitor, and catalyst monitor. These tests are performed only when certain vehicle operating parameters are met. For example, in order for the O2 or evap monitor to run, the vehicle needs to be at a continuous speed with very little throttle movement such as driving on the freeway. If you drive the car continuously in stop and go type of traffic those monitors may never be initiated so they would still show not completed and P1000 would be stored indefinitely.
At the same time though it is crucial that engine be operating in closed loop for emissions/fuel economy reasons. The computer would not care if the evap or catalyst monitors had been completed in order to enter closed loop as they do not effect fuel delivery decisions. His Millenia probably would not pass the catalyst monitor it the O2 sensor downstream from the warm-up CAT had been wired incorrectly. Should have set a code P0160 but again, the early system was extremely primitive for malfunction detection. Comparing a 95 computer in the Millenia to a PCM in a 2006 Mazda 6 would be like comparing Pong to an X-box.

The indication that a CE light would flash for a sensor failure related to emissions is not accurate. The ONLY time the CE light will flash is during an engine missfire that is severe enough that the PCM determines catalyst damage will occur if vehicle continues to be operated. People might ignore the CE coming on solid but are much more likely to pull over and stop if the light is flashing. Manufacturer warrants catalytic converters for much longer than regualar warranty (Mazda is 8 years/80k miles), and they certainly don't want you driving around destroying the CAT that they, the manufacturer, will have to replace for free.

(in reply to keninn)

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RE: Check engine light - 1/16/2006 11:28:16 AM

miss95millenia

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My boyfriend changed my spark plugs and the light went out.

(in reply to VT STANG)

Post #: 7