SB20-H-001

VEHICLES PRODUCED PRIOR TO JANUARY 2, 2019 SOME CUSTOMERS MAY COMPLAIN ABOUT AN ILLUMINATED CHECK ENGINE LIGHT SETTING SHORTLY AFTER STARTING THE ENGINE. IF THE REASON FOR THE CHECK ENGINE LIGHT ILLUMINATING IS DTC P0027, THE MOST LIKELY CAUSE IS LOW BRAKE AIR PRESSURE. DTC P0027 MAY SET WHEN THE BREAK AIR PRESSURE IS VERY LOW OR AT 0 PSI AT THE TIME THE VEHICLE IS STARTED. THE BREAK AIR PRESSURE CAN BE DEPLETED (RESULTING IN LOW OR 0 PSI) AFTER THE AIR SYSTEM HAS BEEN SERVICED OR THE VEHICLE HAS BEEN STORED FOR A LONG PERIOD OF TIME. IF DTC P0027 CONTINUES TO SET EVEN THOUGH THER ARE NO AIR SYSTEM LEAKS THAT MAY BE QUICKLY DEPLETING THE AIR SUPPLY OR CAUSING DELAYS IN THE BUILDUP OF AIR PRESSURE AND THE EXHAUST BRAKE IS FUNCTIONING PROPERLY, FOLLOW THE SERVICE PROCEDURE IN THIS BULLETIN TO REROUTE AIR DRYER LINES FOR IMPROVED AIR SUPPORT TO THE EXHAUST BRAKE.