Customers attempting to order school buses built on GM diesel chassis are in a holding pattern as the auto maker incorporates next-generation selective catalyst reduction technology to meet the upcoming EPA 2010 emissions regulations.

The next-generation diesel not expected until next spring, which equates to an approximate four-month wait for customers.

All orders for current 2009 models have been taken, and manufacturing continues through Dec. 31, at which time engines meeting 2007 requirements will cease production. GM will then retool engine to use urea-based SCR to reduce nitrogen oxide levels by 90 percent.

A GM spokesperson said the new 2010-compliant offering will be introduced by late second quarter of 2010, likely by sometime in February or March.