Valved cat back issue
Thread Starter
Intermediate
Joined: Aug 2024
Posts: 45
Likes: 31
Valved cat back issue
Hey everyone,
I recently installed a valved exhaust system, and I’m having ongoing issues with the check engine light (CEL).
Here’s the full setup:
Anyone run into this or have a workaround? Is this a calibration issue, or do I need a more advanced solution like a simulator?
Appreciate any help or advice!
I recently installed a valved exhaust system, and I’m having ongoing issues with the check engine light (CEL).
Here’s the full setup:
- Valved exhaust system
- afm module connected but (no physical valves installed)
- NPP and AFM modules are connected by wire
- NPP modules seem to be working fine, but sometimes I hear them trying to close one side repeatedly
- Occasionally, they work as intended, but the OBD2 still throws a “valve out of reach” message, especially when the valves are supposed to be closed
- I also did the AFM relearn using a Launch Elite OBD2 scanner, but the CEL keeps coming back
Anyone run into this or have a workaround? Is this a calibration issue, or do I need a more advanced solution like a simulator?
Appreciate any help or advice!
Last edited by shadowhtc; Jul 16, 2025 at 04:53 PM.
Instructor
Joined: Oct 2021
Posts: 234
Likes: 71
From: Ohio
You may have a valve stuck open. I have a Borla Attack and the valve is stuck open, so when it goes to v4 the cel comes back on. But my code doesn'stay outer reach my code actually says valve stuck open.
Livin the Life
Joined: Feb 2021
Posts: 1,687
Likes: 1,800
From: Simi Valley, CA
2024 C8 of the Year Winner - Modified
Thread Starter
Intermediate
Joined: Aug 2024
Posts: 45
Likes: 31
i dont think it is stuck open because it closes but it stutters souple of times then it goes open again and some times it just closes normally
Livin the Life
Joined: Feb 2021
Posts: 1,687
Likes: 1,800
From: Simi Valley, CA
2024 C8 of the Year Winner - Modified
