Code P0446 EVAP System Check Engine Light

[airline tech]

If it stays consistent - reset code and it returns - (after resting) - next day (start-up)
Then for me - its failing the (Rationality Check)

Sometimes - the entry conditions can be confusing (chart above)
I read this as (The test will run - Once Per Driving Cycle) only (IF) the entry conditions are met and if they are not met (the test aborts)
Note: They do not list a voltage (in this chart) so the actual pressure reading is the most important


So - at first start - Key On Engine Off
Measure: FTP (Pressure & Voltage) - Note Readings

Install The Funnel - and Note Readings

If stuck at 2.08 Volts - the sensor thinks there is a vacuum on the tank and it expects to see (0-H20) or close to 2.65 volts

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[rrwhitman]

Thanks for that. I did have the fuel tank pressure PID displayed as well when I was checking the sensor voltage. The software was defaulted to display pressure in Pascals (vice inches of H2O) and I didn't document the value at the time. I can check again but presumably it was indicating a vacuum. From the chart above it seems that +/- 2.0 H2O during the check at start-up (after 4-6 hour soak) will throw the code. I can do more testing after a soak and setting the software to display in H2O. In any case, would you agree that a constant 2.08 Volts from the sensor is enough of an indication of failure to warrant replacement? Thanks again for all of your information!

 

[RangerBill]

Thanks for that. I did have the fuel tank pressure PID displayed as well when I was checking the sensor voltage. The software was defaulted to display pressure in Pascals (vice inches of H2O) and I didn't document the value at the time. I can check again but presumably it was indicating a vacuum. From the chart above it seems that +/- 2.0 H2O during the check at start-up (after 4-6 hour soak) will throw the code. I can do more testing after a soak and setting the software to display in H2O. In any case, would you agree that a constant 2.08 Volts from the sensor is enough of an indication of failure to warrant replacement? Thanks again for all of your information!

At this point, it looks like a replacement of the pressure sensor is required.

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