mcratchet1 Posted December 12, 2016 Share Posted December 12, 2016 hi i have a 2011 mack chu 613 007780 with 128 code spn 5246 will not go over 5mph is there anything i can check myself instead of taking it to the dealer? thanks!! Quote Link to comment https://www.bigmacktrucks.com/topic/47993-help-128-derate-code/ Share on other sites More sharing options...
fjh Posted December 12, 2016 Share Posted December 12, 2016 (edited) Def tank full ??? If the truck is standard try unpluging the speed pu on the trans this will get you to the dealer a little faster 5 mph it is a bit ridiculous they have a derate set so low ! and dangerous if your on a freeway! Edited December 12, 2016 by fjh Quote Link to comment https://www.bigmacktrucks.com/topic/47993-help-128-derate-code/#findComment-354841 Share on other sites More sharing options...
mcratchet1 Posted December 12, 2016 Author Share Posted December 12, 2016 yes def tank is full, dealership is 100 miles away will it effect anything with the speed sensor unhooked? but im trying hard to avoid the dealership Quote Link to comment https://www.bigmacktrucks.com/topic/47993-help-128-derate-code/#findComment-354843 Share on other sites More sharing options...
Mackpro Posted December 12, 2016 Share Posted December 12, 2016 We set up the manual trans trucks so that if the 5 mph derate happens they can unplug the speeding sensor and will only loose a small percent of power . We set the "engine speed at any error" to 2100 rpm. Normally it's set at 1400 rpm. Also if you don't have a laptop with"Tech Tool " on it , there is little you can do but go to the dealer Quote Link to comment https://www.bigmacktrucks.com/topic/47993-help-128-derate-code/#findComment-354853 Share on other sites More sharing options...
fjh Posted December 12, 2016 Share Posted December 12, 2016 5 hours ago, mcratchet1 said: yes def tank is full, dealership is 100 miles away will it effect anything with the speed sensor unhooked? but im trying hard to avoid the dealership Unfortunately chances are the def is not injecting properly and needs repair anyway its only a matter of time that the crystal build up will choke off the exhaust anyway ! if the speed sensor disconnect works bite the bullet and get it in there! Quote Link to comment https://www.bigmacktrucks.com/topic/47993-help-128-derate-code/#findComment-354866 Share on other sites More sharing options...
mcratchet1 Posted December 13, 2016 Author Share Posted December 13, 2016 ok took it mack just needed a software update go figure Quote Link to comment https://www.bigmacktrucks.com/topic/47993-help-128-derate-code/#findComment-354941 Share on other sites More sharing options...
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