Weird trouble code on 98 Accord

@dam

NAXJA Forum User
Hi guys. My wife drives a 98 Accord LX (4-cyl 5-spd).

Last June, while moving to California, the check engine light came on. It first happened at 11,000' up in the rockies, so I figured it was some altitude related problem. I did, however, pull the trouble code, which told me "catalyst system efficiency below threshold" (this being just miles after my cat warranty was up)

I reset the light, and didn't see it again for a month. Same code, reset it again. Then the light would come on every 2-3 weeks. During this time, I had to go through the California emissions test. It passed with flying colors. Not even a little close to failing. Hydrocarbons barely registered (98 Accord is a "low emissions vehicle").

Eventually, the light started coming on every week, then a couple times per week, and now it is coming on pretty much every 2 or 3 drive cycles! It is driving me crazy to have to pull the fuse to reset the light every 2 or 3 times I drive it.

I called the local Honda dealer. They said they'd put it on their computer and charge me $70 to tell me what I already know (catalyst system efficiency below threshold), and that it would cost $1000 to replace the cat! What a ripoff! I'm not going to pay $1k to replace a cat that already gets me past emissions! Of course, the dealership isn't interested in finding any other cause for this problem when they can sell me a part for $1k and spend 20 minutes installing it. There is sort of a conflict of interests there.

Also, since I live in California now, I can only legally purchase an OEM cat (if that is even the problem).

Now, my first inclination would be to say it is a sensor problem, like one of the O2 sensors. However, they have their OWN trouble codes, so one of those codes would probably come up if the sensor was the problem. Are there any sensors that DON'T generate trouble codes (MAF?)???

I appreciate any advice. I basically have no options right now other than ignoring the problem or throwing money at it that probably won't even fix it.
 
a low catalyst efficiency code sets when the o2 sensor in the cat inself does not get the results that it is looking for. Typically if the o2 sensor were to go bad you would get more than one code. What are you using to pull codes? Do you have the capability to monitor the o2 sensor's mv? How many miles are on the honda? And any of the sensors including the MAF will set a trouble code on the obd2 platform.
 
up until last week, I was using a jumper wire to pull the codes. You set the jumper wire in the right holes, turn the key to "on", and the MIL flashes the code at you. Then you look it up in the Haynes manual and it tells you what the code means.

Last week, I checked out an OBDII Autoscanner from Auto Zone and it gave the same result. I was hoping the $170 computer would let me monitor the sensor's outputs, but it looks like it doesn't do much more than my 2" piece of wire and Hayne's manual does.

If the cat O2 sensor were the problem, wouldn't it give me the O2 sensor trouble code instead of or in addition to the cat trouble code?

Somebody today suggested it might be the MAF sensor, but wouldn't that give it's own trouble code as well?

Thanks for the input
-Adam
 
a maf sensor controlls fuel mixture, and yes it would set a seperate trouble code. The best thing to do would be to monitor the o2 sensor in the cat and make sure that it is working correctly. The possibility is there that you may have a bad cat depending on mileage. also check o2 sensor wiring at the cat, make sure that nothing is melted or shorted.
 
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