C5 P0134 Code
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C5 P0134 Code
I’ve got a P0134 code popping up on my C5 after installing long tube headers, no other PCM code. I’ve tried clearing it, but it comes back after a few miles. Planning to get the car on a lift soon to inspect things more closely.
My assumption is that it’s either a bad upstream O2 sensor or a wiring issue—possibly from heat or a pinched wire during the install. I’m also assuming the headers themselves wouldn’t directly cause this code, unless it’s related to sensor placement or extensions.
My assumption is that it’s either a bad upstream O2 sensor or a wiring issue—possibly from heat or a pinched wire during the install. I’m also assuming the headers themselves wouldn’t directly cause this code, unless it’s related to sensor placement or extensions.
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
I’ve got a P0134 code popping up on my C5 after installing long tube headers, no other PCM code. I’ve tried clearing it, but it comes back after a few miles. Planning to get the car on a lift soon to inspect things more closely.
My assumption is that it’s either a bad upstream O2 sensor or a wiring issue—possibly from heat or a pinched wire during the install. I’m also assuming the headers themselves wouldn’t directly cause this code, unless it’s related to sensor placement or extensions.
My assumption is that it’s either a bad upstream O2 sensor or a wiring issue—possibly from heat or a pinched wire during the install. I’m also assuming the headers themselves wouldn’t directly cause this code, unless it’s related to sensor placement or extensions.
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Joined: Sep 2013
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From: Cape Coral, Florida
So you don’t also see a P0154 with your LT headers installation ??…the P0134 is most likely the header installation since the O2 is much further back into the exhaust stream and the engine will run leaner…if you can graph your upstream O2’s you can see how far below 450mv’s they are running on one bank or both…you most likely will just need a tune with these…if a wiring issue you would be seeing either “circuit” high or low DTC and not a “insufficient activity” one…if you have a scan tool what is lambda at idle, cruise and WOT..if greater than 1.0 you are lean…what do your fuel trims looking like ??…the O2 signal and signal ground can be easily checked with a 12 volt test light and a scan tool.
Last edited by C5 Diag; Jul 31, 2025 at 12:19 PM.
