CEL for Cat - Honda Prelude Forum

dallgire · 03-22-2011, 02:01 PM

Alright guys i just bought my 1997 prelude about a month ago now and the check engine light is on. The guy i bought it from told me that it would come back on and it was for the cat like he said. Only problem is that it smells like its running rich and its smoking a little bit. Cant tell if the smoke is light blue or white. So what i was wondering was could the code for the cat really mean that an o2 sensor is bad? Cause the guys on another forum are saying that it could be misreading and dumping too much gas when idling so in return when i hit the gas it burns off the excess gas?

eriane0214 · 03-22-2011, 10:31 PM

if its running rich, you would get black smoke. check your fuel trim on a scanner data. if its bad. check your fuel system, check any leaks, do a compression test. check da o2 n c if its secured on there and clean. check for exhaust leaks. to know if ur cat is bad, hook up a scanner, warm up your car, go on data stream, look on b1s2 (bank1 sensor2/downstream o2). if its bouncing up down like 1.0 v to 0.1 v alot. your cat is bad.

chubbs · 03-22-2011, 11:27 PM

I'm assuming your getting a p0420, which is cause buy a few things.
I've got a gutted cat on my car, and no cel.

Also, check your plugs. One of the tires not being fully pushed down all the way will throw that same code. it happened to me being careless putting my valve cover back on.

Kronn 98SH · 03-23-2011, 05:10 AM

Ok, ignore those posts. ^^^

dallgire, read and follow this:
Another DIY ATTS, ABS, & CEL (Check Engine Light) DTC

dallgire · 03-23-2011, 05:35 AM

Quote:

Originally Posted by Kronn 98SH

Ok, ignore those posts. ^^^

dallgire, read and follow this:
Another DIY ATTS, ABS, & CEL (Check Engine Light) DTC

wow that looks great thanks man i will try that out and post up the problem! then go from there!

dallgire · 03-23-2011, 05:50 AM

of course 2 pin connector is not there! cant find it lol oh the joy!

dallgire · 03-23-2011, 06:01 AM

alright found it!!! It is code 67..... "67 - Catalyst System - P0420 (efficiency below threshold)".....now what lol

chubbs · 03-23-2011, 11:50 AM

P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)

dallgire · 03-23-2011, 01:34 PM

I was told if i put a high flow cat or test pipe on my car it will still throw a CEL? is this correct or can i do that?

dallgire · 03-23-2011, 01:38 PM

can any of these problems cause my car to smoke?

Kronn 98SH · 03-23-2011, 03:15 PM

Yes, a bad cat can cause your car to smoke. Code 67 can also be caused by a bad O2 sensor, although there's only about a 5% chance of that.

A highflow cat may or may not throw a code. However, there are tons of ways around it.

And you're welcome.

dallgire · 03-24-2011, 05:32 AM

Quote:

Originally Posted by Kronn 98SH

Yes, a bad cat can cause your car to smoke. Code 67 can also be caused by a bad O2 sensor, although there's only about a 5% chance of that.

A highflow cat may or may not throw a code. However, there are tons of ways around it.

And you're welcome.

yea thanks again man! so should i replace the cat first im guessing?

dallgire · 03-24-2011, 10:14 AM

CEL 65 - HO2S Heater Circuit Malfunction

disconnect your 2nd O2 sensor and measure resistance between the 1 and 2 terminal of the O2 sensor harness. 1 and 2 are the top two points under the release clip of the harness connector. resistance (ohms) should be between 10-40 ohms, if not replace O2.

also check the voltage and see if it is in these ranges.

Lean - Less than .3v
Rich - More than .6v

^^^^^^^^
This was on another thread is this the correct way to check the secondary o2 sensor? disconnect the o2 and test the ohms then the voltage?