99 civic dx p0141 code.

[fjcrizzo]

So.... i have a 99 civic dx 1.6 sohc. All stock motor and ecu. I recently replaced my entire exhaust with an aftermarket exhaust. It has 2.5 inch pipe from header back including high flow cat basically free flow cat. I replaced both o2 sensors when i replaced exhaust i had a p0141 code. So now after replacing the both o2 sensors i still have this code. I tried swapping sensors putting upper in lower position since both where new. My code scanner will show either o2 sensor in the upper location works fine reads no problems now either o2 in lower location gives me this code p0141. I feel like my problem is o2 not getting hot enough to send a good signal and ecm thinks heater is bad.....?????? I know both o2 sensors work since they read in upstream location. I tried swapping sensors in both locations. I checked number four fuse under dash and its fine. Is there anyway to bypass this code...???? Both o2 sensors read in upstream location plugged into downstream portion of harness so i know main harness wiring is good. I dunno what to do im no amateur this has got me stumped....??

 

[XpL0d3r]

The issue may be with the high-flow cat. The cat is there to covert your exhaust gases from harmful to not-so-harmful, and the sensors are there to make sure the cat is working properly. Because the secondary sensor is behind the cat, it should read much different than the first one. If the cat is too free-flowing or gutted, that difference won't be great enough, and the car will through a CEL.

Look into the o2 sensor non-fouler trick.

Also, where is the secondary o2 sensor bung located? Make sure it's just behind the cat.

 

[fjcrizzo]

the code it is getting is a heater circuit malfunction code.... both sensors are working in the upstream location.

 

[lethal6]

the code it is getting is a heater circuit malfunction code.... both sensors are working in the upstream location.

This code has to do with the o2 sensors. It could mean 1 of 2 things...1) bad sensor or 2) bad ecm. Bad sensor is the more common, but if you are 100% sure the sensors are good it is pointing to a bad ecm then.

 

[young_]

I had a similar problem, and believe it or not, an autozone replacement part didn't work to clear the code. Mechanic friend told me to get an OEM sensor (expensive) and the CEL went away. Just like that.

 

[HeX]

The OEM O2 sensor is made by NTK. Look up the NTK part number and bargain hunt online. I believe itll be around $80.

 

[boricuaPR]

Hi Hex.. I m looking for advice for my car. I have 1996 honda civic hatchback,, stock..no additions. I would like to put like a full swap vtech or b16..dont know much about stuff.
Thanks

 

[lethal6]

Hi Hex.. I m looking for advice for my car. I have 1996 honda civic hatchback,, stock..no additions. I would like to put like a full swap vtech or b16..dont know much about stuff.
Thanks

Start your own thread AFTER you search. What you are asking has already been asked tons of times and you are thread jacking.

 

[young_]

The OEM O2 sensor is made by NTK. Look up the NTK part number and bargain hunt online. I believe itll be around $80.

Man, I wish I knew that back then

 

[fjcrizzo]

Basically..... I know the ecm isn't bad because when I took the upstream o2 sensor and plugged it into the downstream harness and it read fine......


I know for a fact its not a problem with the ecm I have done several tests to confirm this.

I cant get the downstream sensor to read at all...... it says 1.275 volts and is a flat line on the graph on my code reader.

Now keep in mind that either o2 sensor worked in the upstream location no matter which plug they where plugged into for the ecm.

so I tested both sensors in the upstream location and just swapped plugs to ecm back and forth to make sure the ecm is actually capable to read both sensors but only in the upstream location.

what is making this very confusing is that the code indicates that this is a heater circuit maulfunction in the o2..... keep in mind yet again both sensor worked fine in the upstream location.

so from what I can tell the sensor isn't detecting a hot enough temp after the cat.

HOW THE HELL DO I BYPASS THE HEATER CIRCUIT on the o2.... maybe that will help me...

this is very confusing how can both read no problem in the upstream location and neither can read in downstream location.... its like the 02 isn't even reading.

 

[lethal6]

So the control module won't read either one in the downstream, but the control module is still good? Explain where this theory comes to play. If it isn't reading either one in the downstream and they both work in the upstream, then the control module would be the likely culprit.

Again. This code only throws for 2 things or a wiring issue between the 2. Bad o2 sensor or bad control unit.

 

[fjcrizzo]

When I have either o2 sensor in the upstream location I plugged the downstream plugs harness into the o2 while in the upstream location and the ecm is reading the o2 as the downstream 02 on my code reader but the o2 sensor is in the upstream location.

I know this is very hard to understand on the computer.

I took the plug for the downstream o2 that goes to the ecm and with the o2 in the upstream location and plugged into the downstream harness that goes to the ecm.

My code read shows that the downstream o2 is collecting information in the upstream location....

so in conclusion if my ecm was bad I wouldn't have a reading from the downstream harness what so ever if it was bad.

I can get see that the ecm is reading from the downstream harness....

 

[fjcrizzo]

I mean r u saying that if the o2 is closer to the exhaustis reading good because its hotter.

the ecm is not providing juice to the lower o2 to activate the heater for o2 in downstream location... therefore because the exhaust isn't hot enough it doesn't read in the downstream location

 

[fjcrizzo]

I will check for power going to the heater from ecm.... I know the fuse isn't blown for that circuit I already checked that but that doesn't mean theres power