jlee

I am trying to prepare a 2003 Maxima SE for smog in California. Previously, I had a code P0057 - HO2S Heater Control Circuit Low Bank 2 Sensor 2. So I did the non-fouler mod, reset the ECU, and the code still came back on. I had a friend who gave me one of his used Bank 2 Sensor 2 O2 sensor to test with, so I swapped that in on Sunday. After that I was getting 2 codes now: P0057 and P0158.

So last night I went to Autozone and bought a new Bosch O2 Sensor (autozone part number: 15244). I saw that it has thick black sleeves around the wires, instead of red like the pictures. I don't know if that would make a big issue. Although the clip is green. I installed it right after.

I reset the ECU and cleared the code with my scanner just to be sure. I scanned it twice more and I already have P0057 in pending. I wonder if p0158 will come back, but I'll find out tonight when I'm driving home.

What should I tackle next to solve this? I read on this forum that we can just wire in a resistor at 2 of the wires on the o2 sensor harness. Is this true? Also to note that the car is all stock. No modifications. 160k miles and automatic. I have a spare A56 ECU from a 2002 Maxima that I can take in for programming, but that would be my last resort because what if it's not the ecu that is malfunction? My current ECU is A56 as well.

Edit: im guessing the previous owner before had an o2 sim installed. The bank2 sensor 2 harness looks heatshrinked.

maxiiiboy

P0057 indicates a problem with your rear O2 sensor (B2) and/or with the associated harness/connector. You can only resolve it by fixing/replacing one or both of these parts. Check the voltage between HO2S2 terminal 3 and ground: Are you getting battery voltage there? If not, it's the harness, otherwise it's the sensor.

BTW, I just went through my smog check, also here in California. The new rules are: no CEL, and ALL monitors complete with possible exception of the EVAP monitor. My CAT monitor was incomplete. I ended up replacing both pre-CATs. It did cost me $2300.

jlee

So far i have replaced the sensor on b2s1 and b2s2. Only have p0057 now. I tried making an o2 sim, but i dont think it is working. My last choice would be to check the harness now.

maxiiiboy

BTW, they also did visual inspection. Whether they would detect (and the report) a spacer or other mod I don't know. My car has no emission mods. My inspection was at a STAR station.

jlee

Is terminal 3 the black wire? I just checked the black wire with a positive and ground on the battery and I'm not getting any reading on my multimeter. Is this also the wire that runs to pin 47 on the back of the ECU? If so then I am getting voltage on pin 47 ecu side. Seems like a short somewhere after that. I am currently chasing the black wire right now and will be following it up to the firewall. Let me know if I am doing it wrong. Thanks! Btw what color wiring is R/L? I am reading through the FSM.

maxiiiboy

Re. wire coloring: The coloring symbols are described in the GI section of the FSM (see page GI-14; download the FSM from here: http://boredmder.com/FSMs/Nissan/Maxima/). So, R/L is Red with bLue stripe, etc.

From the diagram on page EC-185: The black wire should be ground, and terminal 3 should be associated with R/Y (red with yellow stripe) wire. The diagram also shows you that the R/L wire runs to ECU pin #47.

jlee

Thanks for responding. So I checked R/L on ECU pin #47 by inserting a metal pin and I do get battery voltage there. I also get battery voltage on R/Y at the O2 sensor harness when it is unplugged. Is it safe to say that my ECU is the culprit and should be replaced? I replaced both bank 2 sensors already and p0057 still appears every 2nd cycle when I clear the code.

maxiiiboy

No, it's not safe to assume that, not without a circuit diagram (of the ECU). However, I am not saying that the ECU is good either!
If I were in your position, I would pay the dealer to diagnose the problem. Only Nissan dealers have the equipment to diagnose these more complex problems accurately. They charge a fixed fee, usually equivalent to 1hr of labor cost, or something close. (It used to be like $115, my guess is it's now something like $150, but it depends on location/state). Once you find out what the problem is, you can fix it yourself, or have your mechanic do it, or whatever.

The danger with going ahead on your own and replacing the ECU (or the harness, or both .... ) that you will be just replacing parts, hoping for a hit but you'll miss (trust me, and guess how I know).

BTW, ask them to diagnose ALL problems - and be aware that your car may have more than one problem.

Edit: Well, you can follow the diagnostic procedure on pages EC-186 and EC-187 of the FSM, steps 1-5.