Todd71106 Posted July 2, 2023 Share Posted July 2, 2023 Greetings. I have a 2013 Mack granite with an MP8. Yesterday, the DEF gauge and the oil temperature gauge started bouncing back-and-forth and the engine brake started acting erratic. Sometimes the engine brake works sometimes it didn’t. It’s not slowing the truck down like it normally does. All three events started simultaneously not sure where to start, I’m guessing it’s something electrical. Has anyone had a similar experience? Quote Link to comment https://www.bigmacktrucks.com/topic/72999-2013-gu713-erratic-behavior/ Share on other sites More sharing options...
Mackpro Posted July 2, 2023 Share Posted July 2, 2023 First thing is tighten the battery cables. Anytime the DEF gauge fluctuate, check the cables Quote Link to comment https://www.bigmacktrucks.com/topic/72999-2013-gu713-erratic-behavior/#findComment-534045 Share on other sites More sharing options...
Todd71106 Posted July 3, 2023 Author Share Posted July 3, 2023 11 hours ago, Mackpro said:check the cables I’m on my way down there right now. That’s the first thing I’ll check. That makes sense because I replaced the starter a few weeks ago and had the batteries disconnected. Quote Link to comment https://www.bigmacktrucks.com/topic/72999-2013-gu713-erratic-behavior/#findComment-534059 Share on other sites More sharing options...
Mackpro Posted July 4, 2023 Share Posted July 4, 2023 The ACM (after treatment control module) that runs the DEF system and nox sensors has its own power supply directly to the battery with a small 30 amp fuse holder on top of the batteries. It’s very common for this to be left off or not tighten after a battery change or disconnection. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/72999-2013-gu713-erratic-behavior/#findComment-534165 Share on other sites More sharing options...
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