GM Truck Club
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 6 of 6
  1. #1

    Question Code P0446 Confusion

    '99 Sierra 1500, 4.3l. Problems began this time last year. Several codes came up, including p0446 and a couple of others (misfire & vacuum leak stuff). At that time, replaced plugs, wires, distributor cap & rotor, vapor canister, vc purge solenoid valve (per TSB), gas cap, & intake manifold gaskets. All codes cleared, except for p0446. Scanner indicated 2 codes, p0446 & p0446 pending. Was planning to get another emissions waiver for this year (as we're at a loss as to what to do next), so went to the inspection station & got the truck failed a couple of days ago. Then yesterday, the MIL went out. Was ready to rush back to station to get emissions passed, but decided to scan first. Scanner now gives p0446, but the p0446 pending is gone. Also, MIL is lit (stays on, not like the brief flash of all dash indicator lights) with key in on position, but goes off when the truck is cranked. Previous freeze frame data indicated p0420, & now that pending DTC is gone, freeze frame data indicated p0171 Very confused. Any ideas on where to go from here?

  2. #2

    mfleetwood's Avatar
    Join Date
    Jul 2010
    Denver, CO
    Blog Entries


    I moved your thread here as your issue could apply to more that just your model truck. In widening your audience, you should start getting responses/opinions.

    Welcome to the Club and good luck!

    Mike (Denver, CO) - 2008 Sierra 1500 Z71 SLE 5.3L 4WD

    SUSPENSION: Rancho 4" Suspension Lift; Rancho RS9000XL Shocks; Rancho Skid Plates; Rancho MyRide Wireless Shock Controller;
    BFG All Terrain KO 315/70/17
    DRIVE TRAIN: 4.56 Gears; Detroit TrueTrac Differential; True Cool 40k Transmission Cooler
    PERFORMANCE: DiableSport Predator Tuner; Custom Tuned by Diablew; Magnaflow Exhaust; AFE Cold Air Intake
    ELECTRONICS: Kenwood DNX6180 Touchscreen; Subthump box w/10" Kicker; Driver Information Center (DIC); Rear View Camera
    ACCESSORIES: Westin Brush/Grill Gaurd; Westin Nerf Bars; Truxedo Tonneau; 20% Tint; Tow Mirrors w/Heat & Signals

  3. #3


    Here's a long thread on the topic:

    Use of the search tool on this site may reveal others that are useful, too, and that may be your best bet as it's a springtime holiday weekend in the U.S. and site traffic tends to be lower on busy holiday weekends like this one.

  4. #4


    SurrealOne, thank you for the advice. Researched on the forums and internet prior to posting.

  5. #5

    Join Date
    Sep 2010
    everett, massachusetts


    your problem can be a tough one to fix. some it is just a bad fuel cap. a simple fix. with what you replaced [threw parts at it , no leak testing] this can occur.

    What is occurring most likely is the fuel tank/vapor lines have a leak. the fuel filler can / is a possible item. happened to me at the metal fill neck where the neck had welded metal bracket for mounting. used metal mender.

    If the tank/vapor lines etc has no leaks , then the fuel tank/pressure sender [wires/connector] may be defective. this does occur in the older vehicles.

    The vapor lines being metal and in some areas hard to see need be tested for leaks.

    disconnect both ends plug the line ends and add some air pressure like 3 -5 psi. see if it holds pressure.

  6. #6


    Last year we had some more specific codes & took care of them. Thanks for the ideas. Will let you know results when we get to it. : )

Similar Threads

  1. Code P0446 Confusion
    By treecarp in forum Chevy Silverado Forum (GMC Sierra)
    Replies: 0
    Last: 05-25-2013, 01:53 AM
  2. p0446 code
    By whooper16 in forum Performance & Fuel
    Replies: 0
    Last: 04-09-2012, 03:20 PM
  3. error code P0446
    By snarl2004 in forum General Chevy & GM Tech Questions
    Replies: 3
    Last: 05-03-2010, 08:05 PM
  4. alarm code p0446
    By grubbs11 in forum Chevy Silverado Forum (GMC Sierra)
    Replies: 0
    Last: 03-29-2010, 12:55 PM
  5. '06 Colorado with a P0446 CEL code
    By Boxman7481 in forum General Chevy & GM Tech Questions
    Replies: 0
    Last: 07-22-2009, 07:15 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts