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New o2 Sensor issues P1115 - P1119

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Hi Guys,


I bought a 1999 996 C2 and it now has 135K miles. I lived in a state where I didnt need to smog it for a decade. Now that I live in California, I went to smog the car and had failed due to lean fuel mix issue at slow RPMs on the NOX test. Since the car hasn't had a lot of repairs on it in the last few years, I figured it was time to replace some basic stuff. I ordered a bunch of new O2 sensors off Fleabay and installed them. Boom I now get almost instant P1115 and P1119 codes.


I read Lorans advice on checking the ohms... Here is what my old units read and here is what the new plug and play O2 sensors are reading


Old O2: 2.7 ohms

Old O2: 2.9 ohms


New O2: 4.9 ohms

New O2: 4.8 ohms


The parts have the same part number stamped into the connections. However it's clear that the 996 is extremely unhappy with the new units. I take it that there is no way to reset the ECM to use the new ohms range... Should I replace the old units again until I can source new sensors and make sure they dont have a reading over 2.5? 








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I swapped the old O2 sensors back into the car, and took it for a quick drive. 3 miles down the road I am getting P1124 & P1126 codes currently. I replaced the oil filler cap this week and dont see any intake issues. I will go back over the hoses & clamps but nothing is standing out. 

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Your new O2 sensors' heater elements are not in spec. which is 1.8 ohms ~ 2.5 ohms at 20C

Seems to me your old O2 sensors are fine (otherwise the DME would have thrown the O2 sensor codes).


The P1124 and 1126 mean both banks are too lean (during close to idle engine speed) so you need to check for intake air leak and not enough fuel pressure/flow.

Usually the leak is not from the oil filler cap but from a cracked filler tube (at the cordian). When you remove the oil filler cap, did you feel any suction at all? If not, it's likely the filler tube has crack(s). Of course there are other places that could create intake leak e.g., a bunch of vacuum hoses for the SAI, intake resonance flap, and the vacuum reservoir. All well hidden behind the alternator and throttle body.


You need a pressure gauge to test the fuel pressure and flow. It's also a good idea to replace the fuel filter if it's due.


What are the fuel trims on both banks?

Edited by Ahsai
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It appears to have been a loose hose fitting. I tightened down all clamps, one of which needed 3 extra twists before it was tight. This appears to have stopped the P1124 & P1126 codes. After a 35 mile shakedown cruise, I have one code but it's a P0740 which appears to be a Transmission issue. The CEL hasn't turned on for it (yet). Fingers crossed I can get another 35+ mile run on the car, so it is ready to smog test again. Does anyone know what the minimum miles is before you can get your car tested? The first smog test I failed due to only have 55 miles on the car since I erased the codes.



Edited by JackHBarnes
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My cheapo wired one doesn't have a clue. I have a second Wifi unit which might be able to, it hints at knowing more than the dumb terminal wire version. I also have a BiL who is a partner in an Italian sports car repair shop. WE agree to not ***** each other off much, so out side of OH @!#$, I dont bother him to much on stuff like this.


I will see about a quick and dirty eval from his shops toys this weekend before paying for another failed smog eval.


I am currently fearing that the P0740 will throw a CEL and screw up my next smog window (65+ miles I believe)... Everytime I reset the CEL, I start over... 



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For ipad/iphones, get the OBD Fusion app. For Android phones/tablets, get the free Toque app.

Both are capable of reading the emmision readiness status.

Usually you need to drive the car for both local and highway for a few days before all readiness status are set.

Usually a smog station will check for this reafiness status first and if they see some areas are not ready, they will ask you to drive the car more and bring it back later, as opposed to failing you out right.

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For the wifi unit, do you use iphone or Android with it?

I use an iphone, but the car has a new android touch screen after market stereo with wifi/google apps. I will make sure to get theToque app for the car, and the Fusion app for my phone. Thanks for the advice. 

Edited by JackHBarnes
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Bad news, the OBD Diagnostic Wifi unit, is not compatible with Torque. Which is annoying since I originally ordered bluetooth, but they shipped Wifi, and I said "what ever" at that time. Guess it mattered.


Good news, I ordered two mini blue tooth units that should be here in a week or so. I will install the other in the Wife's 540i V8 6 Stick Dinon, so she can track her toy. 

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  • 2 weeks later...



Sorry for the delay, I ordered a couple of new bluetooth units (wife drives a 540 V8 stick), so I could try bonding them with the car bluetooth stereo. No luck, but I did get them to work nicely with Torque on an Android tablet I have.


So, good news, we have Torque available for feedback. I took the car for about 90 mile run, before the CEL came back on. Torque says that the o2 heaters work, but that the sensors themselves were not Green or Red, it gave a yellow undefined value. 


I have ordered a bunch of o2 sensors off of Flee bay, and all of them were arriving at 4.0 on the Ohm test for the front, and 3.4 ohms for the post cats, when the units in my car are (ALL) in the 2.9 ohm range.


1st question, do o2 sensors burn out and go "high'?

Or do they burn out and slow drop in value?


I was under the impression my 1999 996 3.4l needed o2 sensors with a range of 1.7 to 2.5 each, with my units wearing out to the high side. However, I am not sure about that now that I bought some used units off a 911 with Grade A ratings.


I say this, until I opened my mail, with a low miles 1996 911 (my o2 sensors are the 95-01 gen), in the mail, and it had a reading of 3.9 ohms. Which now makes me wonder if I have been returning all of those 4.0's that would have in fact worked?


That is, is my car supposed to have 2 x 4.0's installed for the precats? 2 x 4.0s for the post cats? For a total of 4 x 4.0 ohm sensors? 


Or am I supposed to have 4.0 front, and 3.4 post cat?


Or am I supposed to have 2.0 rated O2 sensors pre and post? 


The quality A used one in the mail at 3.9 really has me wondering which way O2 sensors wear out now. 





Edited by JackHBarnes
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What codes are back now? If they are 1124 and 1126, please re-read post #3.


We had a cluster, when the CEL came on. I had been driving on the freeway and then got stuffed in a horrible traffic merger event. Basically stuck idling after running nice a warm... 












So, ya. lol... 


MAF was obviously pissed. I have ordered MAF cleaning fluid and will give this one a college try. I have a generic nock off replacement that I chose to not to install after it arrived in the mail. It didnt fit right and put the original back on. I have called the local dismantlers and can pick up one from them for $50 as a test unit before breaking down and ordering a real replacement. I am also getting the tank into the last quarter, where the expected bad water would be the tank that sat in it for a year. It was started and driven around the block and then parked for a period. I havent fully drained that tank or burned it off. I just keep adding new fuel around 1/4 tank. 


I have ordered a new fuel gas cap. I will order the oil filler replacement tonight. Might as well do this stuff anyway. 


My old sensors are giving around the same values, so the computer is able to work as well as it is. I believe once I have the replacement Bosch 4 new o2 sensors installed, it will adjust correctly.  

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It's always helpful to give us all the codes you have :)

Looks like MAF wiring issue. If you use Torque, the MAF reading should be around 3.8g/s at idle with a/c off and engine warmed up.

Everything also points to lean on both banks. I would address the MAF first before anything else.


P0102 Mass Air Flow Sensor – Above Upper Limit

Below lower limit.
– Open circuit.
– Short circuit to ground.
P0150 Oxygen Sensor Ahead of Catalytic Converter (Cylinders 4 - 6) – Intercore Short Circuit or Limited Voltage Increase
Crack in ceramic material
Reference air polluted
Short circuit in signal wire to sensor ground (intercore short circuit).
– Oxygen sensor
– Wiring harness
– DME control module
P1128 Oxygen Sensing Adaptation Area 2 (Cylinders 1 - 3) – Rich Threshold
Fuel/air mixture is so lean that sensing has
reached its rich threshold.
– Intake air system leaking.
– Fuel pressure too low.
– Volume supply of fuel pump too low.
– Fuel injectors fouled.
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BTW, you said "Torque says that the o2 heaters work, but that the sensors themselves were not Green or Red, it gave a yellow undefined value. "

Where did you get these readings? I've never seen color coded readings in Torque. Can you show us a screenshot?

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I have purchased a number of new o2 sensors. I think I have purchased about 8-10 now. lol... Sadly, I returned 3, of which I needed at least 1. Dang It. I am in the process of getting a total of 4 new ones installed and will give you a screen snapshot of what I see. It was a number of smog check off events. Some it could test for, some it couldnt. Some Green and some Yellow in my case. None Red. I will try to replicate and update ASAP. 


Jack "Soon to be Pappy" Barnes

Edited by JackHBarnes
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Sounds like emission readiness flags. With the current various codes, you won't be able to pass these tests or the SMOG check. You can ignore these for now and just focus on the codes, which pretty much tell you MAF wiring issue and the engine is running lean. May also have O2 sensor problem in bank 2 (P0150). The rest of the codes are NOT pointing to any O2 sensors. Rather, they are reporting what the O2 sensors see (extreme lean condition).

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