Some 2021-2022 Envision, CT4, CT5, XT4, XT5, XT6, Blazer and Acadia models equipped with the 2.0L 4-cylinder engine (RPO LSY) may have DTC P0299 (Engine Underboost) set in the Engine Control Module.
If DTC P0299 is set, follow the diagnostics outlined in the appropriate Service Information.
If diagnosis does not identify the source of the condition, inspect the charge air bypass valve (Fig. 7; shown in the fully extended, or closed, position).
Fig. 7
First remove the charge air cooler air inlet hose adapter from the turbocharger. (Fig. 8, #5) Using a bore scope, check the compressor wheel for any signs of damage. If there is damage to the compressor wheel, it will be necessary to replace the turbocharger.
Fig. 8
If there isn’t any damage seen on the compressor wheel, use the bore scope to inspect if the charge air bypass valve is stuck in the open position. (Fig. 9)
Fig. 9
TIP: Be sure to use a bore scope to inspect the charge air bypass valve. The valve may stick open intermittently (plunger is fully retracted) (Fig. 10) and attempting to remove it may cause the valve to return to a normally closed position.
Fig. 10
If the charge bypass valve is found stuck open or is causing DTC P0299 to set intermittently, replace the charge air bypass valve. After replacement, clear any DTCs and evaluate engine operation.
Refer to #PIP5889 for additional information.
– Thanks to Robert Halas
