"Significant cash flows could shift from 2021 to 2022 if we have these work-in-process vehicles held," Jacobson said.
The outlook accounts for a variety of factors that were absent from the first half of 2021, such as rising commodity inflation and lower lease-termination volume. In the first half, GM also benefited from one-time gains on equity investments. All together, the factors add up to $3.5 billion to $4.5 billion in headwinds for the second half.
GM posted $2.8 billion in second-quarter net income, compared with a $758 million loss a year earlier as the coronavirus pandemic sharply cut production.
Last quarter's results were dragged down by $1.3 billion in warranty and recall costs, including $800 million related to the Chevrolet Bolt EV, while robust consumer demand, high transaction prices and strong performance by GM Financial helped bolster earnings, Jacobson said.
Ford Motor Co. last month also raised its full-year earnings guidance to a range of $9 billion to $10 billion, from $5.5 billion to $6.5 billion previously. The company expects volume in the second half of the year to increase by about 30 percent compared with the first half.
Stellantis last week increased its full-year forecast for adjusted operating profit margin to around 10 percent, compared with previous guidance of 5.5 to 7.5 percent.
GM expects to produce about 100,000 fewer vehicles in North America in the second half of the year compared with the first half, with crossovers accounting for most of the lost output, Jacobson said.
Semiconductor manufacturing slowdowns in Malaysia because of the spread of the coronavirus led to downtime at several GM plants during the second quarter. The automaker's pickup plants in Flint, Mich.; Fort Wayne, Ind.; and Silao, Mexico, are scheduled to go back offline this week.
Until last month, GM had kept pickup production humming amid the chip shortage, even building some trucks without certain features.
GM expects chip supplies to improve in the fourth quarter, creating more opportunity for increased output later in the year, rather than in August and September, Jacobson said.
"We don't know that it'll be fully resolved then, but we're being cautious, and we're seeing signs for improvement," he said.
GM could see additional upside if consumer demand continues to rise, Jacobson said. Its average transaction price rose to $48,550 in the second quarter, 12 percent more than a year earlier, according to Edmunds.
GM expects high pricing to continue as dealership lots remain sparse, CEO Mary Barra said.
GM could build more vehicles than forecast, Jacobson said, but that will depend on chip availability and the pandemic.
"I just want to emphasize the caution that we're putting into that" guidance, Jacobson said.
"If the environment abates and this resolves quickly, then I would expect that we would outperform the midpoint."