2004 Saturn Ion P0453 and P0496: Fix for Check Engine Light with Gas Cap and EVAP System Issues
A few weeks ago, my check engine light came on in my 2004 Saturn Ion. I took it to AutoZone and was diagnosed with code P0453, which indicates a high evaporative emission system pressure reading. I checked the gas cap, replaced it, and after that, the check engine light turned off temporarily—but returned a few days later with a new code: P0496, indicating a malfunction in the evaporative emissions control system (EVAP) purge flow. I then visited Goodyear, who replaced both the solenoid valve and purge valve. After the repair, the check engine light went off again but returned shortly after, with both P0453 and P0496 codes persisting. Goodyear suggested resetting the vehicle's computer, but I'm still unsure why P0496 remains active. My question is: Does a faulty pressure sensor need to be replaced for P0453? Or could the issue stem from the solenoid valve or purge valve malfunction instead? I'd appreciate any insights on diagnosing these codes specifically in 2004 Saturn Ion models, especially regarding EVAP system components and how they interact with the powertrain control module (PCM).
A tire shop addressing drivability or emission issues? Unlikely. For P0453: high voltage reading from the Fuel Tank Pressure Sensor (FTPS) — what exactly is the PCM detecting in terms of voltage here? For P0496: the PCM detects purge flow when no purge should be occurring — is the purge valve being controlled correctly by the PCM? I recommend starting with P0453. Use an OBD2 scanner to check for any additional codes, such as P1635 (EVAP system fault). When the key is on and engine is off, what voltage does the FTPS send? The expected reading should be around 1 volt. Have there been any recent repairs or other issues affecting the EVAP system before this?