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P0172 & 0175 codes

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Old Aug 20, 2025 | 08:42 PM
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Default P0172 & 0175 codes

Changed the fuel filter on my ‘02 C5 (128,000 miles) Monday and now getting the above captioned codes. Put approximately 50 miles since and the codes still appear.
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Old Aug 20, 2025 | 08:48 PM
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Originally Posted by Lowrate
Changed the fuel filter on my ‘02 C5 (128,000 miles) Monday and now getting the above captioned codes. Put approximately 50 miles since and the codes still appear.
I assume they are C and not H codes, and when you say the "still appear" ....you mean they come back after being reset.

If so, what is the fuel pressure at the rail.?
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Old Aug 20, 2025 | 09:25 PM
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Originally Posted by lucky131969
I assume they are C and not H codes, and when you say the "still appear" ....you mean they come back after being reset.

If so, what is the fuel pressure at the rail.?
We haven’t had the fuel pressure checked yet. Yes they are C codes and they come up after I reset them. Twice now.
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Old Aug 20, 2025 | 09:50 PM
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Originally Posted by Lowrate
We haven’t had the fuel pressure checked yet. Yes they are C codes and they come up after I reset them. Twice now.
Ok. So you did not have the codes before you changed the filter/regulator assembly, and now you do?


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Old Aug 20, 2025 | 10:16 PM
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Yes
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Old Aug 20, 2025 | 10:55 PM
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Originally Posted by Lowrate
Yes
So it sounds like you got a bad filter/regulator. I would test the pressure at the rail so you have a point of reference. If you replace it get a good brand....absolutely nothing from Amazon or ebay unless you find a trusted seller with NOS.
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Old Aug 20, 2025 | 11:06 PM
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It was a Fram.
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Old Aug 23, 2025 | 08:56 AM
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Several times now, the codes are HC and others are either just H or just C. I can’t get into a shop until next week.
The car runs fine. No black smoke, not sluggish, etc. Any ideas?
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Old Aug 23, 2025 | 10:06 AM
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Originally Posted by Lowrate
Any ideas?
Suggestion was made to check fuel pressue at the rail....did you do that? You have a common denominator here. You had no codes or issues before the filter/regulator was changed, and now you do.

What do you think the most likely cause of your problem is based on the information available?
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Old Aug 23, 2025 | 12:38 PM
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Originally Posted by Lowrate
Several times now, the codes are HC and others are either just H or just C. I can’t get into a shop until next week.
The car runs fine. No black smoke, not sluggish, etc. Any ideas?


Let your shop diagnose it...we can't.



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