On the 2002 GXE 1.8L engine P0057 refers to the s2 o2 sensor heater circuit. The o2 sensor heater operation is sort of mysterious on that engine. It only is heated electrically in certain circumstances. Above 3600 rpm it is not heated electrically. Below 3600 and after driving for 2 minutes at a speed of 43 mph or more it is heated. The code means at times it should be heated, the computer isn’t sensing the current through the heater circuit is correct. Are you sure you have 2 banks on that engine? Most 4 bangers econoboxes only have one exhaust bank.
I’m seeing the o2 sensor in question has 4 pins, 1-4. pin 1 is the o2 sensor output, pin 2 is the heater circuit ground, supplied by the computer at times it should be heated, pin 3 is the heater input voltage, and pin 4 is the sensor ground. So two questions you got to answer first. What’s the resistance between pin 2 and 3 (w/harness disconnected). And with the harness connected, what’s the voltage between pin 2 and 3 at a time when it should be heated?
@Devon_Rogers, you must not have a Sentra because it would not have a bank 2. As for the rest of them, I didn’t see this post back in 2008 or I would have told them that the 2002-2006 Sentra’s had an issue with the connector to the rear O2 sensor. It was located low down near the alternator and would fill up with water, corroding the pins. Replacing the sensor or the ECM would not fix the problem, the connector on the harness side had to be replaced.
Yes I do have two banks, it has California emissions so it’s got more sensors, and a lot more headache! so bank 1 is monitered by cylinder 1&2 and bank 2 is montitoered by cylinder 3&4. I will have to see what the resistance is between the two wires, this is black/white wire and red/white wire? The ground wire and the ground when the ECU switches to a ground.
I have visually inspected the harness and all the conncectors and pins are straight and not a single bit of corossion on any connector. You are sort of correct normally a 4 banger is only monitored by 2 o2 sensors an upstream and down stream sensor, but because it has a California emissioned motor in it, it has a lot more sensor on the motor and just an example is that it has 4 o2 sensors 2 upstream and 2 down stream. If you don’t believe me, I can personally send you a picture of all 4 o2 sensors.
How many warm up (pre)cats are there and what year is your Sentra. I was speaking specifically about the 2002-2006 aka the B15 model, which was the model of the original poster. I could see them putting 2 sensors up stream of the precat but not downstream, unless they put in sensors before and after the clean-up cat. In the B15, there was only on before the cleanup, not one after.
The service data is ambiguous on the one exhaust bank vs two banks issue, but splitting a four banger exhaust system into two separate banks is certainly possible, and would likely result in improved emissions and possibly even better performance. If I had that problem I want to measure the sensor’s-in-question resistances and voltages, as I posted above. I don’t have access to the wire color data, sorry. A Chilton’s or Haynes repair manual would probably have it.