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2004 Buick Rendezvous 3.6L Fuel Evap Codes P0451 and P0446: Diagnosis and Fix Guide

Model: 2004 Buick Rendezvous Fault Code: P0446 Posted: 2018-08-21 10:38

Hello, I'm experiencing two diagnostic trouble codes on my 2004 Buick Rendezvous 3.6L: P0451 and P044-6. When I refill the fuel tank, the engine often fails to start—requiring me to turn the key and press the gas pedal to initiate cranking. On occasion, it cuts off mid-start. I've already replaced the gas cap with a factory-approved one, but I still smell gasoline and notice the vehicle runs roughly. The codes were read at O'Reilly's using a basic scan tool; I initially thought it might be the fuel pump, but that was ruled out. My next step is to schedule a professional diagnostic. The system appears to be related to the EVAP (Evaporative Emission Control) system. Based on common issues with this vehicle model, both P0451 and P0446 can often stem from a faulty fuel tank pressure sensor located on top of the gas tank. These codes typically appear together. However, without access to a proper scan tool capable of performing bi-directional control tests on the EVAP system, it's difficult to pinpoint the exact root cause. If I had to guess, a failing fuel tank pressure sensor is likely. It's important to note that these evap-related codes generally don't affect drivability unless paired with actual leak detection codes. Diagnosing such issues requires specialized equipment and expertise—especially in driveability and electrical systems. I'm considering paying for an hour of certified diagnostic time at a shop specializing in these areas before attempting any DIY repairs.

Related fault codes
P0446P0451
Comments (7)
Anonymous 2018-08-21 12:01

Make, model, and engine size: 2004 Buick Rendezvous 3.6L

Anonymous 2018-08-21 12:06

The vehicle is a 2004 Buick Rendezvous with a 3.6L engine.

Anonymous 2018-08-21 12:58

Do you have access to a scan tool for reading and clearing codes, or did the diagnosis come from a basic OBD2 reader?

Anonymous 2018-08-21 13:02

No, I used a standard OBD2 scanner at O'Reilly's. The codes were confirmed there. I ruled out the fuel pump as the issue. My next step is to get a full diagnostic from a certified technician.

Anonymous 2018-08-21 13:03

The diagnosis indicated an EVAP system fault, which aligns with both P0451 and P0446 codes.

Anonymous 2018-08-21 15:08

Both P0451 and P0446 are commonly caused by a faulty fuel tank pressure sensor located on top of the gas tank. These codes often occur together. Without a high-end scan tool capable of bi-directional EVAP system testing, it's difficult to confirm the exact source. A failing sensor is a likely culprit. However, these evap codes typically don't affect drivability unless paired with actual fuel leak or vapor detection codes. Proper diagnosis requires specialized equipment and expertise in driveability and electrical systems—such as those found at certified shops specializing in EVAP diagnostics.

Anonymous 2018-08-21 15:11

Thanks for the insight! I was planning to attempt a DIY repair, but now I understand it's best to get a professional diagnostic. Appreciate your help!