Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2000 through 2021 GM passenger cars and trucks (including medium duty) with gasoline engines.

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  Buick GM Passenger Cars and Trucks (including Medium Duty) 2000 2021 — — All Gasoline Engines

• The MIL is on and the ECM has P0442 (EVAP small leak detected) and/or P0455 (EVAP large leak detected).

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  Some technicians may find one or more of the DTCs set in the Engine Control Module (ECM): • P0442: Evaporative Emission System Small Leak Detected • P0455: Evaporative Emission System Large Leak Detected

Possible causes

• P0455 sets for a large leak or purge blockage: an unseated tube connection, a damaged tube, a stuck open canister vent valve or a stuck closed purge valve.

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  For DTC P0455 (large leak detected), the vehicle will set the code due to large leak or purge blockage. A large leak can occur from an unseated tube connection, a damaged tube, a stuck opened canister vent valve or a stuck closed purge valve.

• P0442 sets for a small leak, which can come from a stuck open purge valve or stuck open canister vent valve.

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  For DTC P0442 (small leak detected), the vehicle will set this code due to small leak. The leak can occur from a stuck open purge valve or stuck open canister vent valve.

Steps to confirm (in the document’s order)

1. Inspect all purge connections for proper installation and look for damage or wear along the lines; if damage is seen, confirm with the smoke test.

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   All purge connections must be inspected for proper installation. While inspecting the line connections, look for any signs of damage or wear along the lines. If any damage is observed, proceed to confirm via the smoke test.

2. Some leaks show only under pressure and some only under vacuum, so check both ways.

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   Some leaks will only be noticeable under pressure and some only noticeable under vacuum. We recommend checking both ways.

3. Cycling the purge and vent solenoids with GDS2 while inspecting may reveal a sticking valve.

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   Also cycling the purge and vent solenoids with GDS2 while inspecting may indicate a sticking valve.

4. Critical connections 1-3: purge tube to purge valve (at intake manifold), purge tube to chassis EVAP line (rear of engine, near transmission), chassis EVAP line to canister.

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   1. Purge tube to purge valve (at intake manifold) 2. Purge tube to chassis EVAP line (at rear of engine, near transmission) 3. Chassis EVAP line to canister (at canister)

5. Critical connections 4-7: fuel tank load line to canister, vent valve line to vent valve, fuel tank load line jumper connection (near fuel tank), and the fuel tank cap closed properly.

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   4. Fuel tank load line to canister (at canister) 5. Vent valve line to vent valve (at vent valve) 6. Fuel tank load line jumper connection (near fuel tank) 7. Fuel tank cap is closed properly (at refuel compartment)

6. If all connections are good, check the vent valve for a stuck open position.

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   If all connections are good, the vent valve should be checked for a stuck open position.

7. If the vent valve is verified to function correctly, go on to investigate the purge valve.

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   If the vent valve is verified to be functioning correctly, proceed to investigate the purge valve.