There may be possible moisture or condensation freezing in the crankcase pressure sensor assembly on some 2019 CT6; 2019-2022 XT4; 2020-2022 CT4, CT5, XT5, XT6, Blazer, Acadia; and 2021-2022 Envision models equipped with the 2.0L engine (RPO LSY). As a result, DTC P04FB (Crankcase Ventilation Hose Connection Pressure Sensor Performance) may be set.
If DTC P04FB is setting in temperatures below freezing, follow the published diagnostics in the appropriate Service Information.
If a root cause cannot be determined, check the PCV/crankcase pressure sensor assembly. Remove the PCV/crankcase pressure sensor and hose assembly and inspect it for any frozen moisture or condensation. (Fig. 11)
Fig. 11
If frozen moisture is present, allow the crankcase pressure sensor and hose assembly to thaw out and the moisture to drain. Next, using a combination of light compressed air and a shop towel, remove any residual condensation/moisture. Once completed, clear any remaining DTCs using GDS and evaluate the condition.
– Thanks to Robert Halas
