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Discussion Starter · #1 · (Edited)
Ever since I did my exhaust I keep getting the Service Engine Soon Light. I replaced my rear o2 sensor with a simulator and that didn't fix it. Then I replaced the simulator with an AC Delco o2 sensor and the SES light came on again. So I put a glasspack muffler on as a resonator to see if maybe this would fix it. It didn't work. I got another SES light. I'm thinking my high flow cat might be junk so I'm replacing the cat on Monday. I bought my R/T downpipe w/high flow cat used so I'm thinking it's just too worn. Any input here would be great!!!
The SES lights I'm getting are P0420 for bad catalyst and also a P0300.
I have also added my Intense PCM at the same time as the glasspack.
 

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I dont get it either, the simulator should tell your pcm that your cats perfectly fine. I dont get it, whats the other code for???
 

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Discussion Starter · #3 ·
The other code is for random misfires. I put in better plugs to fix that. I put my simulator back in yesterday and so far the light is staying off. Hopefully it stays off.
 

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If it comes back again, try testing the wires between the pcm and the O2 sensor. Check for a short to ground or a short to power with an ohm meter.
 

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Discussion Starter · #5 ·
So far so good. The SES light hasn't come back yet. I'm happy again!!!
 
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