I have a, if you can believe it, black 99 coupe. My check engine light came on. Using the excellent information on this site, I found I had multiple comm errors along with P0420 TWC System Low Efficiency Bank 1-A.
I reset the codes. About 24 hours later, the light came back on. This time only the P0420 TWC System Low Efficiency Bank 1-A error is present.
Can anybody give me some info about this problem? Easy fix? Trip to a dealer? Reset the light and sell the car?
Thanks for your time.
Tim

 

Do you have any header, high flow cats or other exhaust mods? If not, it may be the rear 02 sensor that's starting to go. You may need to replace it.

 

Howdy!

I get this once in a blue moon - I understand with headers and hi-flow cats, the O2 doesn't quite get the right airflow and can indicate a fault. I read that sombody said it's something to do with it heating up properly. This makes some sense considering when mine comes on: looks like it happens when it's cold and rainy. Hadn't seen this error in months, then on the way home the other night it got very cold and was raining and after I splashed through some standing water, the light came on.

I'm the in the process of pulling my cars completely, plugging the rear 02 holes and editing out all the related codes using HPTuners

 

Both of these replies apply to me. I've had my C5 since November and I bought it with a Borla resonating exhaust (no mufflers, twin 4" pipes) system. These messages happened when it got cold (O.K. it went from 70 to 30).
So this code is just part of having a high flow exhaust system? And speaking of my exhaust, I have about had it with the noise it makes. I'm talking about the "howl" inside the car from about 1800 to 3200 RPM. I know what the car sounds like, I want the sound outside the cabin. I like a roar when I get on it but not at cruising RPM. I must admit I do like the extra get up and go. Any suggestions how to keep the (some of) extra HP and lose the noise inside? For less than a grand? I can probably get some trade money for my system (Muffin Mufflers--Austin, TX), but I would like some suggestions from the more knowledgeable folks out there.

Thanks for your time.

Tim

 

Tim

This is what happens when an exhaust system is installed on a C5 with out respect to driveability. The owner of the car before you was able to tolerate the noise and liked the power.

You will find out that you can install a better engineered system, get rid of the noise, STILL have a great sounding system and have little or NO in cabin resonance and loose very little HP.

The ONLY way that you are going to be able to find a system that totaly suits your need is to get a ride in a C5 simular to your set up. If you like it COPY IT!

I have an 02 Z06. I decided to take the plunge into an aftermarket exhaust system. I have a good friend who works at ZIP Products.

I took a GAMBLE on his recommendations to install a COMPLETE Stainlessworks exhaust system. It consist of Long Tube SS headers, random tech high flow CATS, 3" SS mid section with an X pipe and 3" cat back Stainlessworks duel outlet mufflers!

To be perfectly honest, it REALLY sounds GREAT! It has a deep mello idle, very nice part throttle tone and a WICKED WOT snarl! It is NOT too loud (The Wife even loves the sound ) and there in very little in cabin resonance! The resonance was really my biggest worry and on a scale of 1-10 (1 being NO resonance and 10 being BAAAAD!) I would have to rate it a 2. This is a quality system and the headers fit really well! No sparkplug wire issues and they do NOT hang down lower than the stock system.


Try to find someone who has a system installed and take a ride before you invest money in a new system.

Bill

 

Hey Bill,

Thanks for the feedback. I know what I will be doing at the next Corvette Club meeting. More listening than talking.

Thanks for your time.

Tim