my 1999 sierra 1500 has had the entire emission evap control system replaced but the code still keeps popping back up setting off the engine light. does anyone have an idea if puling the battery for a few hours will reset the whole system and clear the code for good?
The Sierra's PCM will clear it self when the issues have been addressed and fixed.
Here's the "official" word on the subject. I'm sure this will take care of it for you.
Subject: LR4, LM4, LM7, L59, LQ9, LQ4, L18 DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Vent Solenoid and Bracket) #04-06-04-055A - (03/20/2006)
Condition
Some customers whose vehicles are operated in dusty type environments, such as farming or mining off-road type applications, may comment about the illumination of the instrument panel SES light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.
Cause
Dirt and dust intrusion into the EVAP canister vent solenoid, resulting in restricted air flow, may cause this condition.
Correction
DO THIS
Replace the EVAP vent solenoid with a more robust vent solenoid.
DON'T DO THIS
DO NOT Replace the EVAP canister or other EVAP parts.
After following the Service Manual diagnostic P0446 and determining that the EVAP canister vent valve is the cause of the SES light, replace the existing EVAP canister vent solenoid and bracket. This new vent solenoid has an enhanced filtering capability and a filter element that can be easily removed and cleaned. To ensure correct installation, follow the procedure below.
Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
Remove the bolt retaining the vent valve bracket.
Disconnect the electrical connector.
Disconnect the canister vent valve hose.
Install the new vent valve bracket, P/N ??????, to the vehicle with the retaining bolt.
Tighten
Tighten the bracket mounting bolt to 12 N·m (106 lb in).
Install the new vent valve, P/N ??????, to the bracket.
Reinstall the electrical connector.
Reinstall the canister vent valve hose.
Lower the vehicle.
Clear the DTC.
Sorry i only have the part number right now for the newer Sierra, but the dealer will have the right part numbers for your 99 Sierra.
