This past winter hasn't been kind to the 2014 Chevy Silverado. Sales of GM's new pickup are down, and big new discounts are on the way. Photo credit: General Motors Co.

Is General Motors (NYSE:GM) giving up on its new 2014 Chevy Sliverado already?

Not likely. But GM is cranking up the discounts on its new truck, at least for the month of March.

Trade publication Automotive News reported this week that GM is planning a huge national promotion for March, in which it will offer big discounts on nearly all Chevrolet models -- including the all-new Silverado pickups.

These pickups were all new less than a year ago. They were designed from the ground up to be more profitable than the trucks they replaced. The new Silverado was supposed to be one of the cornerstones of GM's global push to boost its profitability. 

These trucks were supposed to be good enough to sell without big discounts. And so far, they have: GM's pickup incentives have been lower than most rivals' in recent months.

But now? GM is about to offer some big new discounts, and that's raising concerns.

March is apparently "Truck Month" for Chevrolet
According to the Automotive News report, GM's plan is to stage a major advertising blitz around a "Truck Month" promotion for the month of March. GM has apparently told Chevy dealers to expect an "unprecedented promotional assault," according to the report.

During "Truck Month," Chevrolet Silverados -- and nearly every other Chevy model -- will be available to the public at "supplier pricing," the deeply discounted prices that GM offers to employees of its suppliers. (Only the Corvette and the limited-production SS sedan are excluded.)

GM's "supplier pricing" is equal to the dealer invoice price, plus destination charges and a $150 fee. That's the biggest discount GM has so far offered on the new Silverado.

Why are they doing this? We've heard so much from GM about how the company is determined to be disciplined with its incentives from now on. GM has insisted that it is absolutely focused on improving both its profits per vehicle sold as well as its vehicles' resale values, even if it costs them some sales.

Both of those goals are undermined when discounts get boosted. So what's going on?

Sales are down and inventories are rising
Officially, GM won't comment on any of this. But unofficially, we know that the last couple of months have been rough ones for a lot of automakers. Not just GM, but rival Ford (NYSE:F), Toyota (NYSE:TM), and others as well. All have suffered from the weather; heavy snow and severe cold in many parts of the U.S. have kept car shoppers away from dealerships.

Overall, GM's sales were down 12% in January, but sales of the Silverado were down more than 18% versus sales in the year-ago month. To some extent, that's explained by recalling that GM was blowing out the last of its old-model pickups a year ago. The discounts were huge back then, as were the sales totals. It makes for a tough comparison

Sales have been subdued, though. And now is estimating that GM's sales fell another 5.4% in February. (We'll know for sure when GM reports its monthly sales on Monday.) 

But while sales have been subdued, North America's auto factories have continued to crank out new cars and trucks. That means that inventories are rising. As of the end of January, GM had a 114-day supply of new vehicles. (60 days' worth is considered optimal. Inventories often rise in the winter, but over 100 days is cause for concern at any time of year). And GM isn't the only automaker with this problem.

That has led some analysts, including your humble Fool, to worry that a price war could break out as automakers compete to clear out the rising backlog of new vehicles. That would be great for car shoppers, but bad news for investors: A price war would erode industry profits all around.

Is a rebound on the way?
Officials at Ford have expressed confidence that sales will rebound once the weather improves, and high inventories will fall on their own as the year progresses. That sentiment is shared by some third-party observers, including Edmunds senior analyst Jessica Caldwell. Caldwell told me on Friday that she thinks demand for new vehicles will likely be strong once the weather improves. But, she cautions, it's not a sure thing.

GM hasn't said much either way. But this big new sales event suggests that they're starting to get concerned. It's possible that this event will simply drop GM's inventories enough to put the company in position for a strong spring once demand rebounds.

But it's also possible that we're seeing early signs of a problem, one that could do some damage to GM's bottom line. Stay tuned.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.