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2001 Buick Lesabre P0446 Code: Evaporative Emissions System Fault Diagnosis

Model: 2001 Buick Lesabre Fault Code: P0446 Posted: 2017-08-08 12:33

As a seasoned mechanic with limited experience in electronic systems, I'm troubleshooting a P0446 code on my 2001 Buick Lesabre Custom (3.8L engine, 174,000 miles). The vehicle runs smoothly—achieving 60 mph in under 4 seconds with no hesitation—and I've already replaced the gas cap. I’ve inspected the vent solenoid: applied 12 volts, it clicks properly and airflow is unimpeded. All hoses are intact and show no cracks. Similarly, the vapor canister has been checked—no leaks or damage, and all hoses leading to the front purge valve appear in good condition. The purge solenoid (located on top of the engine) does not click when 12 volts is applied. Additionally, I’m not detecting power at its connection with the key on. The fuse for the vent solenoid (rear fuse box, position #11, 10A) is confirmed good and shows voltage during key-on operation. I'm wondering: Is power to the purge solenoid triggered by a specific condition or system signal? Should it click when powered? And could the FTP (Fuel Tank Pressure) sensor be involved—does it require removing the fuel tank for access? I’ve ruled out major electrical faults and have no other diagnostic codes. Any guidance on how to test the FTP sensor, especially observing pressure changes during vacuum tests with the vent valve opened, would be greatly appreciated. I plan to inspect this component in person next Wednesday.

Related fault codes
P0446
Comments (3)
Anonymous 2017-08-08 13:13

Only P0446 present? With key off and engine off (KOEO), there should be 12 volts on the pink wire of the vent solenoid—located in the rear fuse box, position #11 (10A fuse). After confirming that, check the FTP sensor and monitor pressure changes when vacuum is applied and then released by opening the vent valve.

Anonymous 2017-08-08 15:28

Thanks for the prompt reply. The #11 fuse is good and I do have power at the vent solenoid with key on, as expected. However, I’m not getting any voltage to the purge solenoid—located on top of the engine—and it doesn’t click when 12 volts are applied. This raises a concern: should the purge valve click when powered? The FTP sensor seems like a potential culprit—I believe it requires removing the fuel tank for access. Your suggestion about observing pressure changes during vacuum tests with the vent opened is helpful, but I’m unclear on how to perform that test practically. I’ll inspect this component in person next Wednesday and update accordingly.

Anonymous 2017-08-08 16:17

The purge solenoid should receive 12 volts via the pink wire when key-on (KOEO). Check for any additional diagnostic codes or symptoms. A high-quality OBD2 scanner can monitor FTP sensor voltage in real-time during live data, which may reveal anomalies under specific conditions.