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Volkswagen’s emissions scandal has created a busier online marketplace for the German automaker's used diesel vehicles in the United States.

Online used car marketplaces such as Kelley Blue Book or AutoTrader.com have seen a significant upswing in activity surrounding the specific vehicles affected by the scandal.

"On AutoTrader, we are seeing shopping for diesels up," said Michelle Krebs, a senior analyst at AutoTrader, who noted that the volume of shopping activity between private parties, including purchases and negotiations, is up by almost a fifth over the last week.

This comes as overall Volkswagen shopping across the site — including not just private sales but all new and used sales of Volkswagen models — is down 1 percent within the same time frame, Krebs said.

AutoTrader's sister company, Kelley Blue Book, is also seeing an increase in Volkswagen-related traffic. KBB.com has seen a 79 percent increase in people looking up the trade-in values of Volkswagens with turbodiesel engines on the site. Comparatively, Volkswagen total trade-in value lookups (including non-turbodiesel, or TDI, vehicles) have increased by only 10 percent.

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Krebs said she believes the market is thriving on potential buyers looking for a good deal.

"We often seen spikes in shopping when something is in the news," she said. "Some of that's just curiosity, checking out what the prices are, but there may well be people that are looking to see if people are selling (used Volkswagen diesels) for cheap."

The U.S. online market trends come as there are indications that overall diesel Volkswagen sales are declining in Europe. MeinAuto.de, a German online car dealer, saw a 10 percent slip in inquiries last week, according to Deutsche Bank analysts. Additionally, a U.K. price data firm, Glass, said that Volkswagen TDI valuations fell 0.2 percent in September.

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It's still too early to tell if U.S. Volkswagen owners are using online marketplaces to unload their used vehicles. Krebs said AutoTrader has no data on any increase in listings just yet.

Despite the increases in shopping activity, Karl Brauer, a senior analyst at Kelley Blue Book, told CNBC that the site hasn't seen any substantial or worthy valuation shifts so far.

"I think we see the potential for some downward slippage of values but probably only along the lines of 3 to 5 percent," he said.

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Krebs said the pricing of Volkswagens on AutoTrader.com, both diesel and nondiesel, are a mixed bag.

"It appears private sellers are generally sticking with their prices of the (Volkswagen) diesels they have listed on AutoTrader overall, although they have dropped their listing prices specifically for the Beetle diesel and the Audi A3 diesel some," she said.

In terms of all inventory on the site (new, used and private sales), the Audi A3 and Volkswagen Beetle models saw the steepest decline of all Volkswagen diesel vehicles, dropping $547 and $260 respectively. The Passat diesel dropped only $88.

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While online marketplaces are bustling, VW dealerships have been less forthcoming about sales trends. Dealerships in the New York City area that spoke with CNBC this week had little to say about how businesses was going and directed inquiries to Volkswagen's corporate office.

Volkswagen is expected to introduce a plan to address its emissions technology problem on or before Oct. 7.

Stifel Nicolaus analyst James Albertine told CNBC last week that Volkswagen had already been on a steady decline because of an aging product line, as well as competition from other automakers that are producing fresh models at overlapping prices.