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Discussion Starter #1
As the title says, i have now been getting a code of P0125 after install of ppe headers and catted midpipe. I also installed coilovers today.. If i erase the code it will come back on after about 20 minutes of driving. I have been having codes on and off with the post cat sensor, so i believe this may be the issue.. CAP, i'm waiting on you for this.. After some searching i found that the P0125 code, although said to be a coolant issue, is bogus and has to deal with o2 sensors(i read that from a thread you responded to CAP).

Also, today, after installing the coils and getting gas my car began running like garbage, misfiring like crazy and very rough acceleration.. I pulled over and checked some stuff.. I had a striking suspicion it had to do with the MAF, so i babied her home, and put the stock intake back on(meaning to do this for a while since the research and reading i've done has always said that the intakes are no better than the stock..). This fixed the misfire issues and she was back up and running... I was hoping it would fix the P0125 code issue as well, but no dice.

SO, this brings us back to the original issue of the P0125 code. My current setup is stock intake(no elbow ATM), PPE headers with conditioner harness. full o2 readings on the right plug, conditioned on the left(driver side) plug. High flow cat, and currently have 2 antifowlers with o2(could this be an issue? i left them in to prevent any issue with any CEL). Che lotus style dual canister exhaust.
Thoughts, comments, help? lol
 

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Discussion Starter #4
Thanks t, I'll take a look at them in the am. Coolant levels are good, I checked those. Temp levels are static from the dash temp gauge, aren't precise obviously, but not bouncy or erratic. Ill check levels again tomorrow, 20 minute drive to and from Gf's house, I hope will show me something.
 

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Good Choice going back to the Stock Intake.. With that you can Reset the ECU ( Pull the Battery ) and get the Fueling back to almost Stock, with NO O2's..( Pull the O2 Sensor Plugs ).. if you can't get to the Wiring Right Away..

Then we can Figure out the O2 Problem..

I Think you are Correct about the 125/Vs O2 Code.. It was last reported back to me to be a problem with the LEFT o2 Sensor..


I hope your Only Using ONE o2 Sensor on the PPE, as the Duel Sensor PPE is Trouble..

The Single O2 Sensor that is Installed in the PPE, needs to have it's Blue and White Wires Split, and go to BOTH o2 Sensor Plugs in the Engine Bay..

So the Engine Fuel Choices are being made with ONE o2 Sensor.. that is a MUST for this type of setup..

The O2 Sensor needs to have the Heater Wires Coming from ONE of the O2 Sensor Plugs.. usually the Right Side Plug..

Then the Other O2 Sensor Plug ( Usually the Left ) needs to be driving a 20 to 50 Ohm Resistor.. And it Will get HOT.. so it needs to be left to hang.. and not rattle next to anything..

If you cant get the Resistor, don't worry, as long as the O2 Sensor wires ( Blue and White ) are split between the Two Plugs, the ECU will get the Siginals it needs to make good Fueling Choices..

It will get pissy and toss a heater sig for the Bank that is missing the Heater.. ( 150 I think?? )

No problem with the Last O2 Sensor ( Post Cat ).. it plays no roll in the 125 to 13X Codes, or in the Fueling Decisions the ECU makes..

Cap
 

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Discussion Starter #6 (Edited)
Sorry, I thought I clarified, it is the single o2 with the conditioner. The conditioned signal is going to the drivers side plug(with the resister). Unplugged battery already and reset. Its Running well right now, but it is throwing the code still. you mentioned the 125 could be the left plug which would be the one with the resister in my case. Any correlation? Like I said, I'm going to resplice the harness again tomorrow to clean it up and prevent further issue.
 

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The 125 appears to relate to no or Low Signal from the O2 Sensor.. and the Left Bank needs to be hooked to more than just a Resistor, it also needs to be hooked to the Blue and White Wires of the Right O2 Sensor..

Can you clarify if the Left Bank Plug also has wires going to the Single O2 Sensor, as well as the Resistor..

Cap
 

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Discussion Starter #8
The 125 appears to relate to no or Low Signal from the O2 Sensor.. and the Left Bank needs to be hooked to more than just a Resistor, it also needs to be hooked to the Blue and White Wires of the Right O2 Sensor..

Can you clarify if the Left Bank Plug also has wires going to the Single O2 Sensor, as well as the Resistor..

Cap
The full harness was made to the spec of ppe via the directions provided. The heater has the resister, the blue and white wire is spliced in with the o2 signal of the right plug.
 

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Cap's test subject

The full harness was made to the spec of ppe via the directions provided. The heater has the resister, the blue and white wire is spliced in with the o2 signal of the right plug.
As subject the aforementioned case of the driver side O2 sensor sending a bad signal, Cap is on point here. There needs to be sufficient current running to all stock ECU wires in this setup, the O2 sensor has 4 wires and 4 signals which all need to be dealt with individually or it will not go into closed loop which will give you a 0125 on our car. I have the same exhaust if that helps, stock intake and cat. I think my O2 sensor was damaged during install, replacing with a Denso fixed my problem.

Edit: Measure the resistance on your O2 sensors - should be around 13-16 OHMs between the black wires on the sensor (haven't seen the conditioner but I have to assume they have the same 4 wires to replicate status). Adding an antifowler could have a negative impact in the signal.
 

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. Adding an antifowler could have a negative impact in the signal.

If I read the Post Corectly, the Anti-Fowler's were added to the Post Cat Sensor. So that is not an Issue on the 125..

I have seen the 125 code from both right and left O2 Sensor Problems.. as it's not really a code for the O2's I'm not sure if the Error that tosses the 125 is only for one side or the Other..

I have been able to determine that the 125 deals with the O2 Sensor Sig, and not the Heater.. so the Resistance readings will not help here.. the Wires in question are the Blue and White..

Check the Splicing of the Blue and White ..

Cap
 

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Discussion Starter #11
Driving today, got gas at the station, drove a little, car started to stutter, pulled over and pulled 02 sensor plugs, erased codes, car running better.. After a few minutes first code to come is p0125(coolant) shortly after 0135 and 0155(02 sensors not being plugged in).
 

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To get the Fuel Trims back to Stock, you need to do the Battery Disconectt for 10 Minutes.. else when you Just clear the Codes, the Fuel trims will stay at 'Krappy Running' condition..

Do a Batt Reset.. the Car will start running better, ( with the O2 Pulled), then Find the problem with the Blue/White Wires.. <OR> you have split the Siginal off of a Dead O2 Sensor..

Cap
 

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i am still getting the po125 code even with the sensors pulled....
That is what I would expect, as I think a 125 code is tossed when the ECU does not recieve a good O2 Sensor Voltage..

Cap
 

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Sounds like my case. When i did my install, I had the original sensors in and my car was about to turn 100k, they were due. Drive at freeway speeds for about 10 minutes to see if it gives 0125 again.
 
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