We have a 1998 Accord LX and recently replaced the catalytic converter and the downstream O2 sensor. It's been driven about 100 miles since then, but the Check Engine Light is still on. We had the codes read today, and here's what we got. I did not change out the upstream O2 sensor. Any suggestions would be appreciated.

P0420
P0108
P0141
P1456

Thank you!

 

Were these the same codes which mad you change you cat? What brand cat and O2 sensor did you use? Did you remove the positive and negative battery cables and touch them for around 3 mins for a reset?

 

What codes did you have before the cat and o2 sensor were replaced?

The next step would be to clear the codes, then see which codes return. That may help eliminate some history codes.

 

I think it was the same codes. We took it to AutoZone and the report said it was the cat. Then, a couple of weeks later, the car wouldn't even start. So, we replaced the cat and downstream OS.

Here's the parts we used:
https://www.carparts.com/catalytic-c...her/reph960303
https://www.carparts.com/oxygen-sens...ire/arbh960910

The new Cat had two O2 ports; I put a bung plug in the forward one. I started to replace the upstream sensor, but someone (can't remember who) said I shouldn't need to.
I did remove the battery cable while changing out the parts, but didn't touch the leads. Is that how you reset the codes?

Thank you.

 

I can tell you the car didn't start due to a bad cat or O2 sensor issue. There's something else causing that.

I am not going to tell you to replace your O2 sensor but I will say Denso should be the only brand you use. Also your MAP sensor is bad somewhere along the line you need to figure that part out. You also have an evap leak on the fuel tank side. Look at your fuel cap.

There are many ways to reset codes on a car. I was giving you the easiest way to reset codes that were permanent since you do not have an OBDII reader. The issues you have I am sure are compounded that have caused your car not to start at this point. Could be a bad starter or battery (I'm not there to see the health of your car) Depending on how long you were driving on a bad cat could of made things worse than they were initially. Maybe someone else can give better advise.

 

When the car wouldn't start, we had it towed home (thankful for AAA). I could only get it to run for maybe 15sec. Just long enough to move it to the driveway. After replacing the Cat and O2, it did start and run. Rough at first, but with a little throttle, it stayed running. I didn't think a cat would do that,but it felt like a back-pressure issue. I'm no mechanic, so I don't know.

To reset the codes, I need to disconnect the battery and touch the + and - leads together for 3 min? (just confirming). I'll give that a try next.
I'll also order a new gas cap.

I have a good friend of mine that's a Master Mechanic, and he's mobile (he pulls a fully decked-out trailer with all his tools and equipment). Funds are tight right now and he usually can tell me pretty accurately what's going on; I just hate to bug him when I can't hire him. He may not mind the call, but I don't want to be "that guy", if you know what I mean.

Looking at MAP sensors, I see anything from $18 to $120. Any recommendation on brands? I usually shop RockAuto or CarParts.com. I try to stay local with AutoZone, etc - but my gosh, they're stupid expensive. MAPs start at $110.

 

How long was your light on to start getting back pressure. Driving for extended periods of time with a clogged cat is detrimental to the engine.

With resetting, yes disconnect both positive and negative cables and hold together. If it makes you feel better completely remove the battery first then hold the cables together.

With your MAP it could possibly be good. The code is saying there is an issue in the wire or DME issue. Check your wiring first to make sure there's no break in the wire. Do a test at the plug to ensue you're getting voltage. I would check the gas cap to see if it is sealing. Only you can see if it needs replacing.

 

Or the OP can remove fuse #13 out of the passenger side fuse box to clear the codes. Just so you know there should still be a blue plug under the glove box door edge that you can use a paper clip to jump and give you codes (D4 light flashing). Just a heads up, as Honda used it up thru 2000 or maybe 2002 (it's in the FSM).
Depending on where the OP lives, salt might have rusted the vent lines, causing the vent code. I know I've ran into that on both my 99 and my wife's 2000 Accords (we live in the salt belt). It's also possible that the rubber hoses have cracked, and are causing the code.
Your code P0420 was for the cat convertor or the cat sensor. I've found more often than not it's the convertor, and the sensor (Denso) can be reused. I had that issue on my 99, in that the PO had replaced it with a cheap unit that had clogged. I went with a Magnaflow stainless unit off e-bay, and reused my sensor.
That was 3 years ago. The cat sensor mainly keeps an eye on the cat, and doesn't effect the fuel mixture like the front one does.
I wouldn't replace the map until after I cleared the codes, and let the system cough it up again (if it's really bad it will).
I hope this helps.

 

Thanks for all the suggestions... This was my dad's car, and he left it to my teenage son when he passed away a couple of years ago. My son would drive maybe 20mi a week in it. The CEL came on just a couple of months ago. We live in Texas (Fort Worth), so no salt here.

I did call my mechanic friend. Like you, he recommended I reset the codes and see what it does after that. He suggested a $40 bluetooth code reader from Amazon. He said they're pretty handy to have.

I'll reset the codes and see what happens. Thanks again - you've been very helpful!

 

if your cat was bad you really need to find out what is the cause of it or you will destroy the new one as well. Cat converters don't die they are murdered.you need to have someone who can properly diagnose reading codes is one thing but using live data freeze frame data and fuel trims go a long way .Auto zone just want to sell parts and i really hate everything about that place