I used to run with the Spoon cat by-pass and the Check Engine Light (CEL) came on. I brought it to service and they checked the CEL code and it came back as defective cat due to unusually high/dirty exhaust. This makes sense given that I wasn't running with a cat, and the svc. advisor agreed.

However, I've switched back to my cat and for the first day the CEL was gone. However, after one day driving it came back! I reset the ECU via the fuse method (check FAQs), and the CEL was gone again -- while idling. As soon as I put the car in gear and gave it gas, the CEL came back immediately!

Does anybody have any ideas as to what may be going on and a possible fix to this??

 

Is the post CAT O2 sensor the same part as the pre? Maybe the #2 sensor is pissed off (made to follow a CAT?) because there was no CAT in front of it for a while and it somehow fouled it. I don't know Rich, just a thought.

 

Check engine light, that is one of the biggest restrictions and controls when modifying the car ... I'm not surprised that it went a bit haywire, anyway it's probably quite hard to determine the problem if some good Honda mechanic isn't willing to sit down and help you out. On the other hand, I suggest a Spoon ECU while you're at it ... Since you're doing a Spoon spec setup, you will need it sooner or later. Just my opinion anyway, that is why I always keep my modifications to strictly nothing that will affect the factory ECU's reading, performance until I'm ready for an aftermarket one.

 

I have tried the Spoon ECU and I can't really justify the cost of it for the gains...btw, it also causes the CEL to turn on.

I'm not sure of the sensor setup, RT. But I know there are 2. When the dealer re-installed the CAT, I wasn't there so I couldn't tell you...however, I do have an appt. for them to 'fix' it next Thursday...hopefully it won't cause an arm and a leg!

 

Good Luck Rich, tell us what it was when you find out.

 

Have a service technician pull down the specific code being set off the OBD-II (On Board Diagnosics). Hopefully this will lead to the root cause of your problem. If it is an O2 sensor issue this will readily be known.

Utah

 

Bob the code told them it was a bad CAT. The question is how does the OBD-II system monitor the condition of the CAT? O2 sensor delta? I don't know ............

 

Bob the code told them it was a bad CAT. The question is how does the OBD-II system monitor the condition of the CAT? O2 sensor delta? I don't know ............

RT,

Yes, the OBD II monitors O2 through the change in O2 content before and after the catalyst. No change, bad catalyst.

However, I only saw one o2 sensor on the exhaust system. Did I miss the other?

 

I don't know about Shamu's but the stock system has two O2 sensors (one upstream and one downstream or the CAT).

 

Yup -- I can confirm there are 2 sensors, and the service manual confirms that the CEL is a signal for faulty emmissions.