CERTAIN GRAHAM WHITE AIR DRYER AND AIR DRYER REPLACEMENT ELECTRONIC CONTROL MODULES, MODELS QBA15 AND EC15, MANUFACTURED BETWEEN JULY 11 AND DECEMBER 20, 2006, INSTALLED AS ORIGINAL EQUIPMENT FOR TRANSIT AND COMMERCIAL BUSES AND SOLD AS REPLACEMENT EQUIPMENT. THE ELECTRONIC CONTROL MODULE CIRCUIT CAN FAIL WHICH WILL CAUSE THE AIR DRYER TO STOP FUNCTIONING LEADING TO PASSING OF WET AIR INTO THE AIR RECEIVER TANK DOWNSTREAM OF THE AIR DRYER. IF THE DRYER CONTINUES TO MALFUNCTION OVER AN EXTENDED PERIOD OF TIME, EXCESSIVE AMOUNTS OF WATER CAN ACCUMULATE AND, IN FREEZING TEMPATURES, MAY AFFECT THE PREFORMANCE OF THE AIR BRAKES.