steeler

What Joe said. I've seen bad grounds, weak connections cause this very issue. During cranking voltage can drop too low to start.

Exhaust temp is not high enough, and 260 degrees before cat? That can't be right.. When I have whacky exhaust temps I'm looking at 7th injector, face plugged cat, temp sensors...

Id almost bet a paycheck its cups..

Doozy here, as normal for me. 2016 mp7 overheating in a pull, or during regen. Engine fan will not engage at all for coolant temp, but will for air conditioning pressure, and manually with tech tool. New fan drive, ecu and vcu. Customer had replaced water pump, thermostat, fan drive before bringing it to me. Didn't take long to determine the fan is not speeding up with coolant temp, but appears to work fine with other signals...

I'm still here, but damn that was 4 years ago. I'm trying to jar my memory as to what I did to fix it. I've had so many cluster f jobs since then they all run together. I wasn't keeping very good notes back then. I'll keep thinking!!

Little late to the party here but looks like you're ecu isn't powering up. I usually find that it's missing power or ground. I'd check that first, if you haven't already fixed it. I'm not at work to look up which pins are power and ground right now, but can get that info to you if you need it.

Thanks guys. It can be hard to find good info, or people to bounce ideas off of. There is a lot of good knowledge on this site, if I can contribute and save someone a giant headache I'm all for it! A lot of people think that they have to go to a dealership to get good service, totally false! I worked at a mack dealership, plenty of clowns there just like anywhere else 😂

Got me baffled as well!

Well guys I guess I'm not as knowledgeable as I thought. The engine brake solenoid fixed it. No idea why that only bothered cylinder number 4! I really appreciate the help even if it's only to bounce ideas off of. I'm gonna write this one in my notes, not that I'll forget it lol. So, I'm thinking that by pulling the rocker off to replace the injector, the oil drained out of everything enough that it ran great for 20 minutes or so, leading me to believe that changing the injector was fixing it, when all I was doing was draining oil from the rockers.....

I appreciate you fjh. I'm with you on the software. Just doesn't make any sense. I did tear all the rockers apart and checked everything. I know this engine brake solenoid is bad, has been bad for awhile. Somebody has unplugged the clutch switch, so it wouldn't throw a fault if they switched the engine brake on. Customer wasn't worried about fixing it, but.... It's getting fixed now lol

There is a function parameters reset, similar to the learned data reset. I did not run it long enough with the 1st test ecu to see if it threw the same code, But, I just pulled an ecu off of another 2015 truck in the shop, and the miss is still there with that one. Sooo.... For whatever reason it runs fine with a 2009 ecu, but not one with the correct year. I'm getting ready to put a new engine brake solenoid on it. No idea why that would cause only number 4 to miss, but I'm just about out of ideas.

Sorry for the delay! Yes just came in today, hooked it up, and guess what! Still missing on 4! Hooked test ecu back up, runs great. WTH. Surely there isn't anything parameter wise that got carried over to the new ecu causing this. I'm wishing now that I would have just programed the new ecu without transferring anything at all from the old one, but too late now. Once it's programmed, that's it, can't change anything other than software updates. Really scratching my head as to what would be different with these 2 ecus that could cause a miss on number 4.coming up empty in my head.

Ok, swapped injectors, this time it was missing tight off the bat, same hole. I hooked up a test ecu, although from a 2009 truck, this one is a 2015. Ran great with teddy ecu, hooked up original one, still missing. So... Tried to reflash but tech tool won't allow it since the ecu already has a chassis ID programed, only new control units can be programmed. Software is up to date, so the only way to reinstall the software is to use the replace hardware function, which it won't let me do unless it's a clean ecu. This must be a new thing? I've programmed used ecus before without issue. Looks like I need a new ecu, but I think we are looking at the backorder game now.

Yes sir, trim codes programed every time, along with function parameter reset. I can reflash the ecu. I think I'm going to be headed that direction either way at this point.

Going to swap 3 and 4 and see if the miss goes with it. If it does, then I'm really bumfuzzled as to what is causing it. It isn't throwing an electrical code, just the learning at limit code. Really strange. I'll find out in the morning.