Recently my car threw a P0138 CEL, High voltage Bank 1 Sensor 2. I have had headers and a full exhaust done for over a year now with no problems, no CELs. I have both o2 sensors connected, one before the cat and one after. How could this all of a sudden happen?

I also noticed that when the car is not warmed up, and this only happens sometimes, I have no power in the low rpm band. Its kind of like the engine is choking, then it hits 2k and revs like normal. Almost feels like some sort of vacuum leak? Not sure if it's related or not...

I've reset the ECU and the code comes back. I have checked the wiring to my o2 sensors, it looks fine.

Does anyone have any suggestions?

Thanks

 

have you extended the wiring? how old is the sensor?

<div class='quotetop'>QUOTE </div><div class='quotemain'>I also noticed that when the car is not warmed up, and this only happens sometimes, I have no power in the low rpm band. Its kind of like the engine is choking, then it hits 2k and revs like normal.</div>

the same thing would happen to me until I did my evap mod. it's either one of 2 things. i couldn't say for sure which one it is in your case.

1. Your extension wiring is bad. you either reversed one of the wires like i did. to know for sure you have to have a scantool and use a laptop to check. perhaps the wires came loose, got wet, or are not soldered together. when extending the O2 wires, always twirl the whole thing up in electric tape and solder the connections.

2. Like i've always been suggesting, something wrong with evap relocation. the evap controls a/f mixture and your second sensor is sensing the wrong mixture. it would explain the code not coming up right away.

if you haven't tampered with evap, it's likely the extension.

You have a 1998, so my wiring diagram would be of no use to you. You would have to look it up on hma or use ultratibby's diagram. The to white wires make all the difference and the way I was able to do it was only with a scantool and laptop.

 

I did extend the wiring to the o2 sensor, I soldered and heat shrinked the connections, taped them, and then loomed the whole thing and zip tied it to the underbody. I did this a year and a half ago, and have never had any issues with it, no CELs either.
I did the evap well over a year ago also, never had any issues or CELs.

The sensor is OEM.

I visually inspected the wiring, and it looks OK. I didn't unwrap it and check the connections and stuff though.. How can I test it?
Or is the sensor bad? How can I test that?

Any other suggestions?

 

are you sure you got the wires exactly correct when splicing the plugs by extending them one by one? if you had the wires mismatched the CEL would go on immediately with the oxygen sensor drive test cycle. so that's why i would rule that out.

if you claim there is no problem with evap, or wiring, then the last thing to do is to replace the sensor itself. it could be just that it's an old sensor that came with the car or it overheated. they crap out every 60k-80k or so.

i might be annoying with this evap stuff, but from what i know the CEL isn't going to light up with bad evap connection. especially with a manual transmission. the only reason it would light up is if there is a leak in the system and in my case it did because there were several leaks. let's say there is no leak, the CEL won't turn on but the car will still run rich without you knowing and overtime the second O2 will detect a bad mixture. so the only way to tell is by getting readings from your second O2 through a scantool. of course i'm no mechanic, but at least that is what i've learned thus far.

there is absolutely no way of checking your wiring except for trial and error with the two white wires if the other colored ones match up. i can't be the only one trying to help. c'mon people!

 

<div class='quotetop'>QUOTE </div><div class='quotemain'>P0138 Heated oxygen sensor (HO2S) 2, bank 1 ��“ high voltage Wiring short to positive, HO2S, ECM Oxygen sensor (O2S) 2, bank 1 ��“ high voltage Wiring short to positive, O2S, ECM</div>

I posted all the engine codes under the Engine & Transmission section......does this help out in any way?