TOKYO—A global parts and chip shortage is taking a heavy toll on Japanese firms with seven out of eight automakers seeing global output drop in September, casting doubt over the central bank’s view the impact of supply constraints will be temporary. Toyota Motor said on Thursday it saw global output slump 39.1 percent in September from a year earlier to 512,765 units, marking the second straight month of falls. Nissan Motor’s global output fell for the third straight month by 27.9 percent in September, while that of Honda Motor dropped for a four month in a row, by 30 percent, data released by the automakers showed. The output cuts by the automakers are starting to affect suppliers including Hitachi, which on Wednesday slightly slashed its consolidated operating profit forecast for the current fiscal year ending in March 2022. “The impact of [chips shortages] likely was stronger in the third quarter …