Originally Posted by cleric670

The proper protocol scanner will give you the actual DTC being sent by the ECM. They will be listed in the FSM, an unlisted code is because it's using a different protocol and it's finding the "closest match", P1276 is not a valid DTC for this ECM.

P-Powertrain
1-OEM specific
2-Fuel system
76-specific error

Since it's an OEM specific code it really does need the proper protocol to read it, this is pretty common since there are almost a dozen different protocols, still helps to have something with ISO9141-2 when you're working on these vehicles, it's probably just using ISO14230 which is far more common.

Using a realtime scanner to watch voltage fluctuations will tell you if the sensor is working, since you have drastic changes in performance I'm guessing it's not working at all and when it errors out and "runs better" it's because it is back in open-loop fuel mode.

The downstream O2 sensors are grounded on the black/yellow wire. There's a splice somewhere in the harness but I'm not sure where, they get their ground from the same pin on the ECM. However if you have exhaust leaks that will DEFINITELY cause O2 sensor codes like this but it sounds like your leak is downstream from all this, probably being caused by the hollowed out cats and non-foulers will help get rid of the code usually. Either way you can watch voltage changes on the B2O2 and B1O2 sensors to verify they are cycling as well. Keep the rpm's up at like 4k while you're reading those sensors.

Originally Posted by TheG35Project

I値l check out the voltage fluctuation under load, my little handheld scanner does support live data for the o2 sensors so I値l keep it at around 4K and monitor the voltage. I will be up in my hometown next weekend and will visit my old shop and plug in with their laptop equip with consult. If I don稚 figure it out by then I値l really be able to see everything I need. But I値l go through the FSM and check all grounds and identify correct pin outs on all sensors. Last time I checked resistance and voltage they showed okay but I did not check resistance by the FSM and instead went by the diagram provided by NGK (the manufacture of the sensors I bought)

Originally Posted by cleric670

P1276,P0138, P0158 ?

For the P0158/38

Do the codes come back at idle when you clear them?

If they only come back after revving the engine or driving I would pull the fuel pump and see if the strainer baggy sock is all clogged up.

I'm guessing you already did watch realtime data on the O2 sensors to make sure all 4 are cycling properly?

You should also clean up the two grounds screw points on the front of the engine, top of the timing chain cover, two green screws with a ring terminal landed on the chain cover. One is the transmission, one is the ECM, do them both.

Does your OBD2 scanner handle protocol ISO 9141-2, you really shouldn't be seeing code P1276 on these cars.

Originally Posted by FULLTHROTTLE916

Yes the vehicle is running rich, I have a Snap-On Triton D10, and Osirus Up-Rev software. Both throw the same code(which yes I don't know why the vehicle is putting out a non factory DTC lol), I believe the issue is injectors at this point. I have cleaned, loosened, and re-tightened all grounds including the ones that go to the dash support beam. I took apart my fuel injector cleaner and test bench last night and replaced the cheap pump with a factory DE one lol. Gonna pull the injectors at some point today, throw them on the flow bench and see what's going on. My belief is the ECM is reading B1S1 as rich being the long term fuel trim is too high, thus the ECM is attempting to cut back fuel causing the vehicle to run rough when in closed loop at OT.

I've ran into issues before where the ECM was the issue for things like constant coil pack failure on the same cylinder. So, I even swapped out the ECM, reprogrammed the key, and got the same codes. Interesting they threw the same codes lol. I've gone thru the entire FSM diag procedure and replaced both up-stream's with a Nissan OE sensors(one that wasn't throwing a code was bubbled on one side 😂. )

At this point I'm not even charging the customer anymore, I just wanna know the issue! 😂 I'll update once I throw the injectors on the bench.