Stuominous

I have a D16Y7. Got a new exhaust, nose to tail. Got a header, too. Took it to the shop, they moved the cat underneath with extensions and 2"-2.25" pipe.

Now my check engine light is on. Never was before. The old exhaust fell off. The new exhaust sounds great! But why the CEL all of a sudden?

Help is greatly appreciated!

BryanM.

iTrader: (1)

1. Get the code read and see what it is.

2. Post the code #

Stuominous

Okay. I'll have to track someone down with a scan tool.

slimx

Local mechanic should have an OBDII scanner. Since you changed your exhaust 99% chance it's just the o2 sensor, could be loose, damaged or .. something wrong in someway.

HondaPartsHero

Use a paperclip

https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/how-pull-cel-d4-srs-abs-codes-code-lists-1901557/

nedvalton

In the passenger floor board in front of the door remove the kick panel
find the blue connector.
Insert paper clip or wire in both side forming a loop back
turn key to on position
count the blinks on the cel
long equal 10 short 1
example 2 long 3 short equals 23

Stuominous

Rustled up a scanner today. This is what I got:

P0141
&
P0131

That's the rub! Now how do I fix it?

nedvalton

P0141 is your secondary o2 sensor. The one after the hearder. Could be bad o2 sensor loose wire
p06 31 is low voltage on sensor 1. In the exhaust manifold. Again could be wiring, bad sensor

Stuominous

Okay. No sweat. Just replace o2 sensors and wiring? Sounds mild enough!

nedvalton

Check to see if they removed the #1 o2 that would be the first issue.

slimx

I was spot on - so i take it you'll listen to a little advice.

If the wire seems like it's in good condition, and i say seems because you can't be sure too sure. Replace the wiring.

If the o2 sensor was fine before, it is 90% chance still okay. Unless it was DAMAGED during the installation.

Goto the exhaust shop that fitted the exhaust and make them fix it, as the problem does indeed relate to what they have changed and what they touched/and dealt with.

Stuominous

Okay. Will do. I bought a 36" O2 sensor extension on ebay for $19. Looked legit. I had also bought a 6" and 2 12" ones cuz I wasn't sure how long I'd need it. ...noob

At any rate... I will go to the shop this week and find out what I need to do. Will I have them pay for and replace the O2 sensors and wires? or do I bite it and buy the required parts? Denso? Bosch? Others...?

As long as it wasn't a code for feline rejection (cat mismatch).

HondaPartsHero

Denso

slimx

U shouldn't have bought anything, they are responsible for fixing it, everything included. If you've already bought it though, at least get them to install it for free.

Like i said, tell them to change the wiring, because it's an exhaust shop i doubt they'll have wiring unless they do performance work often. So probably bring wiring too.

B serious

iTrader: (1)

You're implying that an exhaust shop will take responsibility for a CEL brought on by anything except installation?

All they did was install aftermarket parts that were brought in by someone. A faulty O2 extension, cat, or other part(s) isn't their fault.

If they damaged the sensors or damaged the wiring/installed it improperly, they should fix it. That may be the case, but it also may be hard to prove. A damaged or non-working sensor could have been caused by anything.

In either case, if you need a new sensor...buy NGK or Denso. Buy the direct fit sensor. Try rockauto.com or sparkplugs.com.

My recommendation would be not to get riled up into being unreasonable by someone on the internet. It may or may NOT be their fault/problem.

B serious

iTrader: (1)

My guess:

-They put the extension on the wrong sensor lead. So the primary location is now AFTER the cat. This would explain the primary showing low voltage. The cat is scrubbing the exhaust...so the incorrectly placed primary sensor always sees oxygen (low voltage). Although it's surprising that you're not getting a cat efficiency code if this is the case.

-They dropped or damaged whichever sensor has the heater issue. It reads "secondary", but if they put your extension on the wrong lead, the problem could actually be your primary.

Or there is a wire/wiring pin that came disconnected for the heater circuit.

Stuominous

Things just got more fun...

I disconnected the battery thinking a reset might do it. The CEL came back on, so I went to get it scanned again.

The codes before: P0131 & P0141

Second scan (after battery disconnect): P0132 & P0141

I asked him to clear it, he did. CEL came back on. I asked him to scan it again.

Third scan: P0141

So.... What the heck is going on!?

B serious

iTrader: (1)

...did you read anything above?

Or have the car diagnosed by someone?

B serious

iTrader: (1)

...did you read anything above?

Or have the car diagnosed by someone?

Stuominous

Yes. I did read everything. I went back to the muffler shop and asked questions about oxygen sensors and what might be going on. I'm not one to jump to conclusions, so I aimed to find out everything I could about this.

The muffler shop is more than willing to help me take care of this issue. They will install new o2 sensors and extensions if necessary for FREE - which is far more than fair. I did ask them to do an aftermarket upgrade. These things happen. I have to buy the parts. No problem.

The shop suggested I disconnect the battery to see if the computer needed to be reset. I did that. The CEL came back on and I thought it'd be a good idea to rescan to see whether or not the same codes came up. I did that - that's where the second set of codes came in. I thought for a bit more and then asked the guy to clear it. Then that's where the third code reading came from.

I asked the mechanic at work for his thoughts on it. Right now - per his suggestion - I'm going to get an ohm meter and check my wiring.

The problem that seems to exist now is the downstream sensor with the code P0141. If there's a problem with the sensor and/or the wiring, can I use an EX o2 sensor on this? Or is there a better way to ensure correct voltage is sent to the sensor?

I'm going to root this out before I jump around and get all bent out of shape over it. My problem is I don't have the time available to have my car be down for a full day. I'm fairly resourceful and easy to teach on these things. I come here because there are people who know more about all of this than I do.

B serious

iTrader: (1)

The EX and other 4 wire civic/integra O2 sensors are the same. So using one or the other won't make a difference in voltage.

If your code is coming on right away after resetting the ECU, then it means that there is an open or short in the wiring. Usually, if there is a problem that exists with a slow sensor or a bad cat, it takes a drive cycle for the ECU to set a light.

Stuominous

Oh... Okay. Could you explain this 'drive cycle' thing to me? How long is it?

The CEL comes on right away. I put an ohm meter on the extender and the reading came back good. The downstream sensor is now getting hot. I'm probably just going to replace that today. Get it done and over with.

With only throwing a P0141 now, is it safe to assume that I won't have to muck around with the upstream sensor?

B serious

iTrader: (1)

Drive cycles take a couple of days depending on how you drive. You can also do it within a day or less.

Basically, if the ECU sees a condition where a sensor is working...but the reading doesn't make sense in conjunction with the readings from other sensors, it will go through a drive cycle and if that sensor isn't acting right by then....it sets a light.

So your codes for primary high/low voltage MAY or may NOT come back.

The secondary heater code seems like it comes on right away. This means that there is an open or short in the circuit.

You checked the heater OHM readings? They should be like 10-30 OHM, IIRC.

Stuominous

No, I didn't check the heater OHM readings. The muffler shop did me a favor and put the car on the lift and we poked around for a bit. He found that the wire of the o2 sensor was a bit warm. I've also been smelling that ... 'interesting' smell of heat and hot electronics. I put my multimeter on everything except the sensor.

Possible diagnosis: Downstream sensor is burnt. I'm planning on getting one today. Denso for sure. I'll let you know what the prognosis is after the surgery.

Thanks for the drive cycle info.

Stuominous

The downstream was burnt. I went and replaced that. Then the upstream was throwing a code P0132. I gave up and replaced that one. Put Denso in both spots. The flange between the 4 to 2 was a bit loose and separated a bit. Bringing extra oxygen in and screwing up exhaust all over the place. Retightened that down really good and the muffler shop put and extra bracket on the header down pipe to reduce vibration.

No CEL. Runs great. Now I can finally move on to swapping this transmission, clutch, and flywheel. Thanks for your help, everyone. I really appreciate it.