Headers caused CHK ENGINE LIGHT ???

[flipz_ny79]

I just installed the RPW header and now my check engine light is on. Since the front O2 sensor is stuck on the manifold, I ended up buying a new one, it was about that time anywayz (90,000 miles ). My question is, is there anyway to check the O2 sensor to see if its bad. Or would it possibly just be the new header. I got a 96 galant cali spec, and I think it has the ODB II on it. Any suggestions would be greatly appreciated.

[Kain]

Did you reconnect both O2 sensors? You have two of them. I guess if the headers have some sort of flaw in them, or were not installed properly it might cause the CEL. But, as far as I know the only things that will throw a CEL as applied to the exhaust system is the O2 sensor. Either too high voltage or too low voltage. Meaning either they are disconnected or bad, or there is a leak and pure outside air is fouling the sensor signals. With the car running, check for exhaust system leaks by ear. It's pretty easy to hear them. Also, recheck that the connections are solid. Even try unplugging them and replugging them in. See if that fixes anything.

[flipz_ny79]

OK I checked the O2 sensors and for leaks, everything seems to be installed properly. So I was thinking, maybee the header is making my car run to lean that my ECU cant compensate to raise the fuel ratio enough, leading to a check engine light. Do you peeps think a fuel pressure regulator will help any ??? Or would you guys think that something else is causing my check engine light to go off !!! Any response would be very much appreciated.

[Jesse]

Did u try resenting the ECU, maybe it hasn't adjusted yet to the change and resenting the ECU will clear it and it won't come back.

[flipz_ny79]

Do you mean resetting? Ive tried disconnecting the battery, but itll only work for like an hour or so. After that itll come right back on. Isnt there another way to re set an ECU with a comp. or something, dealing with the ODB II systems???

[pinoyesv6]

are u sure u got the o2 sensors in the right order?

[Jesse]

Yeah, if you put them in the wrong order, then it'll get a higher voltage at the 2nd one and it'll throw your CEL.

[flipz_ny79]

Well I only replaced one of them. Iam probably gonna get my car on a lift so I can check for proper installation of the second O2 sensor, maybee it got pulled lose when I got my flexpipe costumized. If that doesnt work Ill just get my ECU zeroed out. Hopefully one of these works. THANKZ for the advice fellaz!!!

[Kain]

I don't think you can get them in the wrong order. The wires aren't long enough to switch them. And I'm not sure on the Galant, but on Hondas they come out of the wiring harness at completely diffrent places. Uhh, try checking to make sure nothing else was disconnected in the process. Also, I just thought of something... you said only one O2 sensor was replaced. That right there might throw your ECU into cataclysm. One sensor is gonna be giving a reading vastly higher than the other, making the computer think something is wrong. You're probably gonna have to replace that other sensor.

[cantbeatmy97]

best thing to do is hook up a scan tool to it and see what code it throws out if its the o2 since u replaced it u can just clear the code

[Jesse]

Also, I remember hearing that near the 2nd o2 sensor ther needs to be a certain bracket in order for the exhaust system or o2 sensor to be properly grounded. If it doesn't get the necessary ground, maybe it's not recognizing enough voltage. Also, the 2nd o2 sensor MUST be before the cat if it's still on there.

These can throw a CEL as well.

[flipz_ny79]

Ok, I had my car scanned and it showed up with 2 codes:
1). P0136 - O2 Sensor Circiut Malfunction (Bank no.1 Sensor no. 2 )
2). P0141 - O2 Sensor Heater Circuit Malfunction ( Bank no.1 Sensor no.2 )

I also erased the codes off the memory but the CEL came right back on later that night. I just wanted to know if you guys could suggest something, before I go ahead and replace that O2 sensor. Also before I do that Iam probably gonna get it on the lift to see if it got cought on anything and got damaged. Thankz !!! And does anyone know wich wire out of 4 on the sensor is for the heating circuit? Thankz again !!!

[krazienluv10]

is this common to have new headers and da engine light turns on??

[manybrews]

its ALWAYS common to have aftermarket parts cause problems.

but in this case, theres a chance the rear sensor is just broken. ive replaced hundreds.


make SURE its fully plugged in before replacing..... ive also had many that were barely attached, and a bit of "messing" around with the exhaust caused it to seperate.

[JiP]

Ok headers are very unlikely to throw a CEL and have exhaust leaks won't do anything either. And its physically impossible to hook up the sensors in the wrong order as someone said...The ECU uses the upper O2 first one in the exhaust stream to calculate A/F ratio and the 2nd o2 is there only to check that your CAT's are doing there job. The other day I was workin around the exhaust pipe 2nd o2 area and when I started the car I threw a CEL that o2 sensor died for whatever reason ...but its no important at all has no engine function whatsoever. I dont even have catalytic converters on my car so if it wasnt for my custom built downpipe having air leaks...I would be throwing a CEL anyway because both o2 sensors would be reading too close to the same voltage level meaning the CATS where not doing there job cause there are non!

[manybrews]

<div class='quotetop'>QUOTE(JiP)</div><div class='quotemain'>Ok headers are very unlikely to throw a CEL and have exhaust leaks won't do anything either. </div>

actually, one of the most common sources of "O2 sensor" codes is from upstream exhaust leaks. they can and do effect it more than any other factor, with the exception of a total failure of the o2 sensor itself.

[JiP]

Ye but the leak has to be significant enough to let out so much exhaust or let in so too much fresh air that its completely dropping the o2 readings. In either case you would notice it because you would definitly hear it.

Bank1 Sensor 2 is the second o2 isnt it..you said you had a replacement sensor for it, you can throw it in, if not I would just leave it as it has no real function engine control wise.

[manybrews]

<div class='quotetop'>QUOTE(JiP)</div><div class='quotemain'>Ye but the leak has to be significant enough to let out so much exhaust or let in so too much fresh air that its completely dropping the o2 readings. Â*In either case you would notice it because you would definitly hear it. Â*

Bank1 Sensor 2 is the second o2 isnt it..you said you had a replacement sensor for it, you can throw it in, if not I would just leave it as it has no real function engine control wise.</div>
you can have a leak that you cannot hear that will effect the performance of the O2, but thats not really the issue.

why would you intentionally remove it, or the cats? besides the legality of it, removing the cats will give you nearly no increase in performance, and if your "check engine" light is always on, you wont know if other issues crop up.

[JiP]

The original reason I removed the cats was becuase it was on a list of things to inspect causing my bad gas mileage. My car revs faster, and does have a little more kick in it so I'm keeping the cats off.

And no the check engine light is not on all the time, I have been running my homemade downpipe with nocats for about 2-3 months now, and the CE light only came on about 2 days ago because I was fidling around the 2nd o2, I think I might have damaged the wire on it but havnt bothered to check it out yet. Whenever I do throw a code I drive with my datalogger hooked up, so if any other codes are thrown i'll see them, but right now its too cold out here to be outside screwin with o2 sensors.

Datalogger is one of the best tools I've purchased. That and a 3' breaker bar. lol

[JiP]

I finaly got a chance to go and pull my drivers side kick panel off If you remember my last couple of posts I had the same error you do second o2 sensor failure. Anywayz, I know the o2 sensor didnt justup and die that easily. I unplugged the harness for it, gave the wire a few tugs and plugged it back in. Turned my car to the ON position, plugged my datalogger in, cleared the error codes, set it to graph both o2 sensors. When I had the CE light on, o2 sensor 2's graph was at all 0, I dont know if the sensor actually wasnt outputting or if the ECU because of the CE light just didnt bother reading it. But anyway, the sensor is working fine just as it was before and the CE light never came back on.

So maybe you wana try what I did and tug the wire a big and then plug it back in, then have autozone clear the code for you, or disconect your battery for a few seconds to clear the code.