(Reuters) - Shares in Germany's Daimler Truck fell as much as 4.2% on Wednesday after the company reported lower than expected margins on trunks sold in Europe and said that its guidance for the year was now "under review".

The maker of Thomas Built school buses and Starline freight trucks also reduced the book value of its Beijing Foton Daimler Automotive unit, triggering a one-time 120 million euro ($131 million) hit to earnings (adjusted EBIT).

Overall earnings of 1.17 billion euros for the second quarter missed expectations by 91 million euros, slightly less than the value of the writedown.

Analyst Fabio Hoelscher of Warburg Research said, however, that Daimler Truck making less money on each truck it sold at its Mercedes-Benz business, which sells in Europe and has Germany as its largest market, was the likely driver of the shares falling.

"What's negatively surprising now was the weak margin in Europe, 6.5% versus 8.7% consensus", he said.

"The China thing is clearly negative. But looking forward, because hopefully investors always try to price in the future, it shouldn't have much of an effect. The asset has been underperforming anyway", he added.

Europe and North America are Daimler Truck's most important markets by some distance.

Its Trucks North America business accounted for about half of Daimler Truck's earnings in 2023, with the European Mercedes-Benz business accounting for 40%.

Trucks Asia, which includes China, was just 4% of earnings last year.

Daimler Truck posts full results for the second quarter on August 1.

($1 = 0.9150 euros)

(Reporting by Louis van Boxel-Woolf; editing by Philippa Fletcher)