- Faulty oxygen sensor: The oxygen sensor monitors the amount of oxygen in your vehicle's exhaust to help the engine control unit (ECU) adjust the air/fuel mixture. A faulty oxygen sensor can cause the ECU to provide too much fuel, resulting in increased fuel consumption.
- Leaking fuel injector: A leaking fuel injector can cause excess fuel to be sprayed into the engine, leading to increased fuel consumption.
- Clogged fuel filter: A clogged fuel filter can restrict the flow of fuel to the engine, causing the engine to run rich. This can also lead to increased fuel consumption.
- Faulty thermostat: A faulty thermostat can cause the engine to run at a lower temperature than normal, leading to increased fuel consumption.
The codes P1441 and P1621 indicate the following problems:
- P1441: Evaporative Emission Control System Incorrect Purge Flow
- P1621: Engine Control Module (ECM) Theft Deterrent Fuel Enable Signal Circuit
These codes are related to the vehicle's emissions system and can potentially affect fuel efficiency. It's important to have these codes diagnosed and addressed as soon as possible.
To address the increased fuel consumption and the trouble codes, I recommend that you take your Pontiac Sunfire to a qualified mechanic or automotive technician. They will be able to diagnose the exact cause of the problems and make the necessary repairs.
