Replaced braided steel connector between exhaust manifold and piping and muffler gasket (PIA as the bolts snapped and had to be drilled out). Smoke tested with no exhaust leaks.

I had the Bank 2 O2 sensor out already so I swapped with Bank 1 sensor.

P0151 cleared replaced with P0131. I had an O2 sensor on the shelf so I replaced sensor and now I have no DTCs.

However....after 30 minute test ride

B1S2 running at a near constant .7V. B1S1 looks good .1-.8V peaks and valleys.

Bank 2 combined FT is -2.2% (ST 2.3/ LT -5.5%) which has me scratching my head in comparison to O2 sensor voltage.

Bank 1 combined FT is 0.8%.

Thanks!

 

You have three O2 sensors. B1S1 (drivers side pre-cat), B2S1 (pass side pre-cat) and B1S2 (post cat, on some model years this is B1S3 and some model years have 4 sensors with B1S2 and B1S3).

Both pre-cat sensors should switch between 0.15 and 0.85V at about one hertz at idle with around 100ms rise and fall times after they are warmed up and you are in closed loop (O2 sensors control fuel delivery). Sounds like B1S1 is good but you did not report B2S1.

B1S2 is the post cat sensor and it monitors cat converter efficiency. When the cat is cold the voltage tracks the upstream sensors but as the cat warms up and starts working then that sensor settles down to an almost steady voltage somewhere between 0.5 and 0.7V unless there is a problem. This is due to the cat's oxygen storage capacity making it act like an oxygen capacitor if you will (as apposed to a flux capacitor).

Your fuel trims are excellent.

If your B2S1 waveforms are proper then it looks like your fixed. Good work swapping sensors and watching the problem follow the bad sensor to confirm.


George

 

I am getting a P0155 and after not starting for two weeks battery is dead. B2S1 O2 sensor has continuity. Voltage and combined fuel trim (<+/-2%) both look good on live data. Ground in O2 sensor cable to PCM? Thanks!!

 

P0155 is the heater circuit on B2S1 (passenger side pre-cat). The PCM detects that it takes too long for that sensor to come online and it assumes that the reason is a faulty heater circuit (wiring, sensor, power or ground) which is used to warm the sensor up faster than from just the initial exhaust heat. Usually this means that the heater circuit in the O2 sensor has failed but it can also mean that the heater electrical circuit is faulty.

The key is to test the ability for that circuit to supply the current and voltage necessary to run the heater. Thats why we use an incandescent test light to simulate the heater load because it draws some current. Disconnect the harness at the sensor and probe the light green/white and light green wires with the incandescent test lamp and see if you get a bright steady light at key on (or start if thats what tuns on the heater circuit). You can compare the test light behavior to the same circuit on B1S1. The heater itself inside the O2 sensor is a simple resistive heating element that should measure between 10 and 25 ohms. At 20 ohms that would draw 0.6 amps or 600 ma at 12V which is around 7 watts. This gives you an idea of what the heater coil should measure and what test lamp bulb wattage is appropriate to test. This Amazon example uses a 3W bulb which will load the circuit at around 50% which is reasonable:



George