Do you have a scan tool capable of reading live data? Another possibility, but rare, is that there is an issue with one of the Catalytic Converters but only on one side. This causes a difference in air flow to each bank of the engine, causing one side to send skewed data to the ECM. You can manually check the Bank 1 front oxygen sensor voltage with a multimeter to see if the voltage level is low causing the code. Since no oxygen sensor heater codes are setting, most likely it is working, If the heater circuit was down for that oxygen sensor it would not reach operating temperature.
To check the oxygen sensor circuits the pink wire and the Black/White wire are the heater circuits, if you back probe the connector on those 2 wires you should have 12volts with engine running. Measuring across the Purple/White wire and the Tan wire you should read the oxygen sensor voltage signal. It should be swinging from 0.2 to 0.8volts normally. You should be able to catch this with a multimeter. The code suggests that the voltage is stuck low, this can happen if the signal wire is shorted to ground somewhere. I would also do these checks on the Bank 2 front oxygen sensor and see what's happening there,
When you cleared the codes, how fast do they come back? Do any codes come back with just the key on engine off?
If there isn't a sensor issue or wiring issue an imbalance in air flow will need to be checked by doing a back pressure test at each front oxygen sensor opening. If back pressure on either side of the engine is more than 1 to 1.5psi that is a restricted exhaust. And causing air flow more on one side of the engine, but we'll check that after wiring and sensor testing.
The 2nd diagram shows the MAF sensor (bottom right), on the Pink wire should be 12v feed with key On using the Black/White wire as a Ground, and a MAF signal on the Yellow wire, but service info wants you to check the MAP sensor signal at Hot idle since this vehicle has both a MAP and MAF. The MAP sensor is on the top rear of the Intake manifold. It reads direct manifold vacuum. The MAP sensor has 3 wires, the grey wire should be 5volts key On, you can use the orange/black wire for a Ground to check the 5volt Reference. At hot idle the Map should read 0.8 to 2.0volts on the light green wire using the orange/black wire for Ground. The MAP sensor reading will tell us if there is an issue with manifold vacuum.
Since you have replaced the MAF already and the oxygen sensors, I think you'll find that the MAP reading should be off, I understand this is a lot of circuit checking. I think you should check the MAP and verify the 12v feed to the MAF and make sure it has a good ground. But the code is a slow frequency code, so there is less air flowing causing this, you're not getting any circuit codes. The same with the Oxygen sensor, its frequency is slow, setting this code, the lean to rich swings of the oxygen sensor is too slow.
Sorry for the long post, but this can be a complicated diagnosis if the air flow is the issue like I think it might be. If you do have a scan tool with live data, the MAF signal should be around 5.4grams per second at idle (3 to 10g/s), about the same as the size of the engine is a rule of thumb.
This is a lot to take in, so do some of these checks and see what you are reading at some of these sensors.
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Monday, March 13th, 2023 AT 8:23 PM