Here's an interesting problem....

[civiceater]

First off my car is a 2003 Nissan Sentra SE-R Spec V with 49xxx miles on it. Original everything except for the mods. I/H/E. (The problem didn't come up until a couple of months ago and I had the H way before it.)

The problem is I pulled a 0031 code, which is a H02S1 HTR (B1). That code tells me that it has something to do with my 1st O2 sensor (bank 1) and it's a O2 sensor heater problem. I was told that if my O2 sensor at least the 1st one or bank 1 has a problem, my gas mileage is crap, which my teacher confirmed. However, it's not. On the QR25DE, I know it's around 23-28mpg and I've gotten a 170 miles on half tank which tells me I'm really doing well on MPG since I usually get 150-160 miles at that mark when I didn't even had any mods.

Now my next theory I thought was it could be electrical. So I looked up the FSM and saw that it could be a fuse. I checked it and well enough it was blown. So I replace it with the same amprage (SP?), then I cleared the codes by taking the negative cable off overnight. The next day I started the car and see; The code was cleared. I drove it to autozone to check if they had an O2 sensor for me (at this point I started thinking I might need to replace it). And sadly they didn't have one so I go home. As soon as I started the car the SES light came up. Again with the 0031 code. I double checked the fuse again and it was blown again. I cleared the code, I put in a new fuse and as soon as I hit the key onto ACC it popped.

So the next thing was to replace the O2 sensor. I went great lenghts to get a used one. I did the same procedure, plug the new one, cleared the code, put a new fuse in and started the car. I still have the code. I thought the "new" old O2 sensor is bad, but I just gotten 190 at half tank which is the best mileage I've seen in the 2 years I've owned the car. Now I have 2 good O2 sensors (1 in my car and 1 in the box) and I'm stumped. I don't know where else to go. I'm going to the dealer on the weekend to see if they could look at it but before that I wanted to go thru you (NISTECH) and others of what you think.

Thanks.

PS. I bought the silver warranty package, will having little less than 50k just got me out of luck on warranty?

[NISTECH]

warrenty on O2 I think is 3/50 emissions warranty but not 100% on that. I have seen this problem and it was due to a screwed up driver in the ECM which is a 8/80 item. Although I have yet to see it actually blow the fuse. you need to ohm check the heater circuit in the O2 though and make sure its not shorted internally. Go to the section in there manual where it has the diag for the code. There should be a wiring diag. Use that diagram to test the O2 heater circuit with an ohm meter. You are testing only the 2 thicker lines on the diagram. When you see the thicker lines in the manuals under code diag that means those wires are the only wires that could set that code [as far as wiring goes] The components could be at fault to which is why you need to test them. If your O2 sensor is not shorted internally you have a short in the wire between the fuse and the O2 sensor in the harness somewhere.

[civiceater]

I was reading it and understanding the FSM. I also found that "thick" wire on the diag, where a few other board members have told me about. I believe it was terminal 2 & 3 on the O2S. I have yet to try to test it since it's already dark and I don't have a garage I could work on. Maybe tomorrow. Thanks. I'll update you if I find anything else.

[s13sr20chris]

one ghetto thing to try is to unplug the o2 and turn the key on. if it still pops you may even want to unplug ecm(carefully!) and turn key on to see if she pops.

[civiceater]

one ghetto thing to try is to unplug the o2 and turn the key on. if it still pops you may even want to unplug ecm(carefully!) and turn key on to see if she pops.

You mean the fuse? When you say unplug the O2, at the manifold or just at the harness connector?

I just tested one part of the FSM's diag for the code

The first procedure was to check the O2S's terminal 3 with power. I tested my multimeter with just the car battery and I got 12v so that I know it's a good meter. Then I tested the O2s and I came up nothing. The FSM said to turn the key to "on" which I had.

I followed the FSM's diag procedure to go with "NG" (I believe for No Good or Not Good) and onto the next one which is just checking the harnesses:

Harness Connectors M19, E108Harness Connectors E9, F47Fuse Block (J/B) connector M115A FuseHarness open or short between O2S and fuse

I found all of those in the diag however, the only thing I actually know that's on the car is the 15A Fuse. How do I find them and how do I check them? Do I use the same method of trying to get power from each of them when the key is "on"?

[NISTECH]

whoa back up here. You thourougly confused me with that post. lets see if I can break this circuit down for you and make it easier, I hope. You have a fuse blowing because a) your O2 is drawing way to many amps.b) you have a direct short to ground in the wire that goes from the fuse to the O2. What you need to focus on is how much resistance your o2 has on the 2 terminals the thick wires go to. There should be a "component inspection" procedure some where in that code diag. You will be measuring the resitance of the heater in the O2 with it UNPLUGGED. The 2 think wires in your diagram lead to those terminals on the O2. Figure out which 2 terminals that is on the o2 and check its resistance.

If the resistance comes out ok per the component inspection. leave it unplugged and turn your key on see if the fuse blows then. If it does there is a short in that one wire. try wiggling the harness while the key is on and see if the fuse blows. If it does that wire needs to be looked over for the short.[that is a real task]

[civiceater]

whoa back up here. You thourougly confused me with that post. lets see if I can break this circuit down for you and make it easier, I hope. You have a fuse blowing because a) your O2 is drawing way to many amps.b) you have a direct short to ground in the wire that goes from the fuse to the O2. What you need to focus on is how much resistance your o2 has on the 2 terminals the thick wires go to. There should be a "component inspection" procedure some where in that code diag. You will be measuring the resitance of the heater in the O2 with it UNPLUGGED. The 2 think wires in your diagram lead to those terminals on the O2. Figure out which 2 terminals that is on the o2 and check its resistance.

If the resistance comes out ok per the component inspection. leave it unplugged and turn your key on see if the fuse blows then. If it does there is a short in that one wire. try wiggling the harness while the key is on and see if the fuse blows. If it does that wire needs to be looked over for the short.[that is a real task]

Alright, sorry about the last post, this is all too confusing to me as well. Now I just unplugged my O2s, replaced the bad 15a fuse on the fuse block by my steering column and when I was about to test the harness for voltage, the fuse popped on me. So I can't even figure out which wire is bad, but seeing as the fuse popped at the initial turning the key on "ON" position, would that tell me it has something to do with the fuse block itself? thanks

[NISTECH]

If this happened while the O2 was unplugged it is somewhere in the wiring between the fuse and the O2. If you look at you diag at the top of the page is the fuse. the wire coming off it has a color listed you need to find that wire at the O2. and start checking the wiring from there to the fuse panel. A good location to check is where the main harness goes through the fire wall.

[civiceater]

Found the problem. Funny and quite puzzling though. In the FSM diagram there's an F22 (O2s harness connector) and an F47 which is part of the whole harness, just a cut or something. The funny part is whole system have continiuity from the F22 to the fuse box, however it also has continiuity to ground which puzzles me. How could that happen? I mean if I have short to ground, then all currents should just go to the short for the "easier" path right? but it's going to the O2s connector as well. Like a split on the road and the current goes thru both of them. Which is weird to me. I guess I need to read about that type of things. But yea I found where it is by process of elimination. I disconnected F47 and turned the key "on" with a new fuse and I didn't blow it so I went ahead and connected it and soon enough when I turned the key to on, the fuse blew. Thanks for the help.

[NISTECH]

Did you find the exact location of the short yet?

It is very easy to have continuity to ground and have continuity to the other end of the harness. If the wire insulation rubs through it will contact ground somewhere. But also it is still intack and contiues to the other end of the circuit. When you do a continuity test it is basically like this. You put one lead on the end of the wire , that lead sends out a probe looking for the other lead, as soon as it sees that lead of your meter it goes right to it. There is no current or voltage being sent it is mearly a continuity check. Simply put is this connected at both ends. It does not stop for the short.

[civiceater]

Did you find the exact location of the short yet?

It is very easy to have continuity to ground and have continuity to the other end of the harness. If the wire insulation rubs through it will contact ground somewhere. But also it is still intack and contiues to the other end of the circuit. When you do a continuity test it is basically like this. You put one lead on the end of the wire , that lead sends out a probe looking for the other lead, as soon as it sees that lead of your meter it goes right to it. There is no current or voltage being sent it is mearly a continuity check. Simply put is this connected at both ends. It does not stop for the short.

I see...I have yet to find the short/ground yet. I'm sure if I take the time to actually strip the whole thing or at least get the wires out of the wire loom to look at them, then I could get the ground out. Btw, is there a better way or the right way to look for the short/ground? Cuz I found the section where it IS so that should make it easier.

Did you find the exact location of the short yet?

It is very easy to have continuity to ground and have continuity to the other end of the harness. If the wire insulation rubs through it will contact ground somewhere. But also it is still intack and contiues to the other end of the circuit. When you do a continuity test it is basically like this. You put one lead on the end of the wire , that lead sends out a probe looking for the other lead, as soon as it sees that lead of your meter it goes right to it. There is no current or voltage being sent it is mearly a continuity check. Simply put is this connected at both ends. It does not stop for the short.

[NISTECH]

usually you can find it by following the harness till you find the spot where it looks worn through. Since you have narrowed it to a section of harness start at the connector and work your way to the o2.