Basically, the availability of cylinder deactivation for the 5.3-liter V8 will be significantly reduced, resulting in a reduction of 1 mpg combined for affected models. This applies whether that engine has the six- or eight-speed automatic, as well as to both the regular Active Fuel Management and the more advanced Dynamic Fuel Management cylinder deactivation systems. DFM does remain with the pairing of 5.3-liter V8 and 10-speed automatic that comes standard on the LT Trail Boss and High Country.
"Due to the micro controller shortage, the components that control AFM/DFM in the engine control module (ECM) have been removed," GM spokesperson Michelle Malcho told Autoblog. She also indicated that the engines will still have the AFM/DFM hardware in place, but that GM will not allow activation of the systems in the future with an ECM change.
Malcho also confirmed to Autoblog that the Silverado and Sierra's other engines will continue to have AFM and DFM, including the 2.7-liter turbo inline-four, 4.3-liter V6 and 6.2-liter V8. In an earlier statement to Reuters, she declined to say the volume of vehicles affected.
"By taking this measure, we are better able to meet the strong customer and dealer demand for our full-size trucks as the industry continues to rebound and strengthen," Malcho wrote Reuters in an email.
The change runs through the 2021 model year, she said.
Malcho told Reuters it would not have a major impact on the Detroit automaker's U.S. corporate average fuel economy (CAFE) numbers.
"We routinely monitor our fleet for compliance in the U.S. and Canada, and we balance our portfolio in a way that enables us to manage unforeseeable circumstances like this without compromising our overall (greenhouse gas) and fuel economy compliance," she said.
GM's fleetwide fuel economy in the 2018 model year was 22.5 miles per gallon and was projected to rise to 22.8 mpg for 2019, according to a report by the Environmental Protection Agency.
To meet federal CAFE requirements, automakers like GM often use credits from either earlier years where they faced less stringent rules and performed better than the requirements or buy credits from other automakers.
GM said last month the chip shortage could shave up to $2 billion from this year's earnings. It subsequently said it expected global chip supplies to return to normal rates by the second half of the year.
The shortage, which has hit automakers globally, stems from a confluence of factors as carmakers, which shut plants for two months during the COVID-19 pandemic last year, compete with the sprawling consumer electronics industry for chip supplies.
GM shares were down 1.7% in morning trading.
(Reporting by Ben Klayman for Reuters in Detroit, additional reporting by David Shepardson for Reuters in Washington; Reuters editing by Nick Zieminski and Jonathan Oatis)