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Fuel Pump Trips Frequently with P0446 and P0451 Codes - Diagnosis and Solutions

Model: Unknown Fault Code: P0446 Posted: 2019-11-25 20:48

My vehicle consistently trips the fuel pump shut-off during refueling. After adjusting the flapper in the fill pipe, the issue persists — the nozzle still shuts off mid-fill. The check engine light displays both P0446 (Evaporative Emission System Vent Control Circuit Malfunction) and P0451 (Evaporative Emission System Pressure Sensor Circuit Range/Performance). Has anyone encountered this symptom? What are the most likely causes? Thanks in advance, Fred

Related fault codes
P0446P0451
Comments (7)
Anonymous 2019-11-25 23:34

The evaporative vent valve might be stuck closed, which can trigger the fuel pump to shut off as a safety measure.

Anonymous 2019-11-26 07:32

Please provide your vehicle's year and model. GM had known issues with early-generation vent solenoids becoming clogged, leading to a TSB that recommended replacing the vent solenoid with one featuring a remote filter. A restricted charcoal canister could also cause these codes. If you share the details, I can help assess whether this applies to your vehicle.

Anonymous 2019-11-26 07:35

I found my model is a 2010 HHR — what engine size does it have?

Anonymous 2019-11-26 15:41

Thanks for the clarification. It's a 2.2L engine, automatic transmission, no turbo.

Anonymous 2019-11-27 08:38

A blocked vent line or charcoal canister is likely the root cause. Diagnosing this accurately requires a bi-directional scan tool to monitor system pressure and valve operation. As a temporary fix, you could remove the vent hose and charcoal canister and blow compressed air through them to clear any blockages.

Anonymous 2019-11-27 08:57

Thanks for the helpful input. I'll look into accessing a bi-directional scan tool and update this thread once I've tested the solution.

Anonymous 2019-12-01 00:27

Try removing the charcoal canister and blowing compressed air through it to clear any internal blockages. This may resolve the P0451 and P0446 codes.