I have a 98 coupe and the check engine light came on. So I took it to the dealership and they ran a check and said that a sensor in my cats was bad and I should replace the cats??? That doesn't sound right to me, there are O2's behind the cats. Wouldn't I replace those? Also, just bought a Magnflow catback and X pipe, so I am wondering what I should do. Any help would be greatly appreciated.

 

...helps to have the codes..

 

Yeah, I didn't get those from them.

 

From Bill Curlee

READING YOUR Engine Diagnostic Codes



The Diagnostic Display Mode is entered with the following procedure:
1) Turn on the ignition but don't start the engine.
2) Press the RESET button to turn off any warning messages. (i.e. door open, trunk open ect)
3) Press and hold OPTIONS
4) While holding OPTIONS, press FUEL four times within a 10-second period.


Initially, on-board diagnostics go into an Automatic Mode which shows diagnostic codes in a pre-set sequence: PCM - TCS - RTD - BCM - IPC - RADIO - HVAC - LDCM - RDCM - SCM - RFA. All codes will be displayed for each. ( i.e. PCM = 4 codes) If none are present in a given module, you will see No More Codes on the display.
There are two kinds of diagnostic codes, Current and History designated with a letter suffix, “C” or “H”. A current C code indicates a malfunction is present and active in the module displaying data. A history code indicates a problem existed sometime in the last 40 or 50 ignition cycles. When not accompanied by a current code of the same number, it's potential evidence of a previous problem, now resolved, that was not removed by clearing the codes.
More likely it's an indication of an intermittent malfunction.
Intermittent codes are the most challenging of the diagnostics. An intermittent code may have happened once, may have happened more than once but is inconsistent or may be happening on a regular basis but not at the time the codes are displayed. History codes can also be caused by a current malfunction in a system that is not operating at the time codes are displayed. An example is the rear window defogger which doesn't operate until the Body Control Module detects engine rpm. For history codes set by a module that does not operate with the key on and engine off, a special diagnostic tool called a Scan Tester is necessary to properly diagnose the malfunction.
Once the system has displayed all modules, it goes into the manual mode which allows selection of each module using combinations of Driver Information Center buttons. Manual mode can also be entered during the automatic sequence by pressing any button except English/Metric (E/M). Once the display shows Manual Diagnostics, select a module by pressing the OPTIONS button to go forward or the TRIP button to go back. Once a module is selected, a code is displayed, and if more than one are present; press GAGES to go forward or FUEL to go back.
To exit the diagnostic mode at any time, press E/M. If you want to erase codes in a given module, press and hold the RESET button To reset the codes once in manual mode, press and hold RESET until it displays NO CODES Press OPTIONS to go to the next module. Repeat the steps until you have reset the codes in all the computer modules.
NOTE!! Only reset the codes IF you want to - it is NOT necessary to do this. Clearing a code does not repair a problem. You are simply erasing the evidence of it in the module's memory. If you clear the code/s, and extinguish the Check Engine Light, your emissions status ready will NOT allow you to pass an emissions test until you have completed the required driving cycles.
Once you have the codes, the next question is: What to do with the information?
First, consult the factory service manual. Any serious C5 Do-It-Yourself owner should invest in the Corvette Service Manual of the appropriate model year. The Service Manual is really a requirement if you want to understand and work on your C5. You can GOOGLE the DTC and also find information on it.




Here is very good site that explains the DTCs:



http://www.obd-codes.com/trouble_cod...d-ii-codes.php



Make sure to include the H or C suffix!!

 

thanks I'll give this a go and see what it gives me!

 

lemme know what you end up with, can stop by and i'll read the codes out and take a look/clear them as well. If you're getting COT (cat over temp) then it probably really IS time to replace the cats.. I happen to have a set of cats extra here, as well as a set of "Cats" too, and can help you with codes you get...

 

Hey thanks for the offer. I'll let you know what happens. I'm actually installing my CLB tonight.

 

something i need to do, first i need to get it out of the 'pull key wait...' -> 'service column lock' cycle


good luck, lemme know how it goes.

 

How many miles on the car? Cats don't usually go bad on these vehicles.

 

90K, I pulled my codes and only have historical ones showing now and none of them had to do with the cats or O2 sensors.

 

Replace the rear O2's first...

or

Tune them out...

When cats go bad, they kill the O2's...

Peace
Chip

 

I'm installing a Magnaflow cat back and X pipe this week, so should I just have them tuned out? I installed my CLB last night and now I'm not getting any codes or CEL??.....

 

My CEL came on again now. It's code PCM 0430-TWC System Low Efficiency Bank 2. Is this a bad cat? I am trying to figure out the best plan since I am installing a new exhaust.