Check Engine Light: Code P0442 on Engine Scanner.

[aarias298]

Hello all, well my check engine light went off the other day and was kinda scared about it because I have an 08 tc and it's basically brand new there shouldn't be problems with it. I got a family mechanic to check it out with the engine scanner and it showed "P0442 Evaporative Emission Control System Leak Detected (Small Leak)" My mechanic asked me if i pumped my gas with the car on and I don't. He mentioned that it could be that my gas cover wasn't tightened. Everytime I pump gas I make sure the cover clicks when i turn it. Im not sure if it may be the stock cover is bad or not. My dad had the same thing happen to his 98 Nissan Altima and tried the gas cover and it didn't work. He told me some sensor was bad and had to change it. If you guys can give me some advice please let me know. Im really trying not to go to the dealer where they will charge me an arm and a leg. I been there before for other things.

[navylife59]

First let me say, if you are the original owner or not, the car is still covered under the full powertrain warranty. Evaporative emissions are fully covered under that. Speak with the Service Manager at the Dealerships in your area to ease your mind.

MIL (Maintenance Indicator Light) will come on and log a DTC (Diagnostic Trouble Code) when certain conditions are met or not met. These can be momentary soft codes that will reset themselves to null when the trouble condition is no longer. Some codes are hard codes which must have the condition repaired and be reset by a Toyota Certified Technician with specialized equipment. Your code is most likely a soft code. Evaporative emissions are constantly checked and will throw a code. However, this code will be stored, cleared from the regular scan, and the MIL turned off if the condition is corrected.

The maintenance manual has a lengthy description on the Evaporative System, it's monitors, and trouble codes. Although there is no P0442 DTC listed, the DTC P0441 is directly related. Possible causes and the description of the monitor is listed below. It is possible that your gas cap was cross threaded which would still give a click but would allow for a slight leak. The Purge VSV could also be a cause as they have been known to fail or could have a loose vacuum line.

1. Purge VSV
2. Connector/Wire harness (purge VSV ECM)
3. ECM
4. Canister pump module
5. Leakage from EVAP system

MONITOR DESCRIPTION
5 hours*1 after the ignition switch is turned off, the electric vacuum pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.
HINT:
*1: If the engine coolant temperature is not below 35°C (95°F) 5 hours after the ignition switch is turned off, the monitor check starts 2 hours later. If it is still not below 35°C (95°F) 7 hours after the ignition switch is turned off, the monitor check starts 2.5 hours later.

[aarias298]

Thank you Navy...So far it hasn't come back on. Im guessing the next time it comes back on I should call my dealer and ask to speak to the service Manager. Like you said if it's under warranty it should be fixed without a charge. The car is two years old and approaching 20,000 miles. One last question can this small leak have an affect on the pistons possibly miss firing. I've noticed a very very slight change in the humming of the engine. I mean it might just be me being anal about the sound. It's a very small change, i know my parent's car is miss firing and it feels nothing like there car.

[navylife59]

The ECM is a learning computer. As such, it makes continual changes to the engine's performance according to the data that it is receiving from the sensors. Bad or inferior gasoline can cause a change in performance giving the motor a different character. This is especially true when you get gas in your tank that has alot of water in it. I would not worry so much about this DTC unless it becomes a more prominent cause of your MIL. Remember, the Dealership can only work on what they can duplicate in the shop. Intermittent errors are hard to troubleshoot so they will tend to push you off as they can't duplicate.