TOKYO, Feb 6 (Reuters) - Japan's Nikkei average fell on Thursday in a choppy session, erasing earlier gains as investors stayed cautious before the U.S. nonfarm payrolls report due on Friday, offsetting buying in companies with strong earnings prospects like Mazda Motor. The Nikkei ended down 0.2 percent at 14,155.12, hovering near a four-month low of 13,995.86 hit the previous day. Mazda Motor Corp ended up 4.3 percent after soaring as much as 7.1 percent to a one-week intraday high after the carmaker raised its annual operating profit forecast by 12.5 percent to 180 billion yen ($1.8 billion). Investors remained cautious with the U.S. nonfarm payrolls report looming on Friday as last month's surprisingly low jobs number was discounted by many as an outlier negatively affected by the severe weather. On Wednesday, the ADP National Employment Report showed U.S. private employers added 175,000 jobs in January, just shy of analysts' expectations. The Topix ended flat at 1,162.37. The JPX-Nikkei Index 400, an index launched this year comprised of firms with high return on equity and strong corporate governance, dropped 0.2 percent to 10,506.11.