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I have a 2003 GMC Sonoma that popped the p0442 "Small Evap Leak Detected" code.
I replaced some vacuum lines in the engine compartment, replaced the purge solenoid and still got the code. So then I start to look at the vent solenoid. I inspected the hard plastic vacuum lines from the solenoid to the canister over to the fuel pump (from what I could see without lifting the bed) and those seem in good shape. Removed the vent solenoid, no cracks, bench tested it with 12V successfully, and blew air into it while it was closed to verify no leakage. So then I started to look at the connector to the vent solenoid. The wires seem intact, and when I start the truck I get ~14V at the connector unloaded. As soon as I plug in the vent solenoid the voltage drops to about 0.1V and there is no click. The coil impedance is around 22 ohms. I had the old purge solenoid available (coil still worked), plugged that in with the same result, voltage drops, no click. Purge solenoid coil impedance is ~19 ohms so not too far off load wise. I suspected a bad ground, followed the wiring harness to the rear of the truck and cleaned the two ground connections there. One other thing to note, I noticed when I was filling the gas tank the other day I heard a high pitched whistling coming from somewhere between the gas tank and the vent solenoid (couldn't confirm where). I reset the codes again and will drive it to see if it comes back but in the meantime:
Questions:
1) Does the voltage at the connector seem to be behaving correctly?
2) Is the whistling sound just from the vent solenoid when its open and the truck is off?
3) What else should I be checking? I haven't yet committed to doing a smoke test, I don't have a machine and not ready to drop $100 to have it tested at the shop yet.
I replaced some vacuum lines in the engine compartment, replaced the purge solenoid and still got the code. So then I start to look at the vent solenoid. I inspected the hard plastic vacuum lines from the solenoid to the canister over to the fuel pump (from what I could see without lifting the bed) and those seem in good shape. Removed the vent solenoid, no cracks, bench tested it with 12V successfully, and blew air into it while it was closed to verify no leakage. So then I started to look at the connector to the vent solenoid. The wires seem intact, and when I start the truck I get ~14V at the connector unloaded. As soon as I plug in the vent solenoid the voltage drops to about 0.1V and there is no click. The coil impedance is around 22 ohms. I had the old purge solenoid available (coil still worked), plugged that in with the same result, voltage drops, no click. Purge solenoid coil impedance is ~19 ohms so not too far off load wise. I suspected a bad ground, followed the wiring harness to the rear of the truck and cleaned the two ground connections there. One other thing to note, I noticed when I was filling the gas tank the other day I heard a high pitched whistling coming from somewhere between the gas tank and the vent solenoid (couldn't confirm where). I reset the codes again and will drive it to see if it comes back but in the meantime:
Questions:
1) Does the voltage at the connector seem to be behaving correctly?
2) Is the whistling sound just from the vent solenoid when its open and the truck is off?
3) What else should I be checking? I haven't yet committed to doing a smoke test, I don't have a machine and not ready to drop $100 to have it tested at the shop yet.