Wasteman1

Replaced the DEF pump and it is still doing the same thing. took back to the dealer. they said the CAC is cracked. they changed that. nothing. now they say the SCR is bad. i doubt it but that's what Mother Mack wants them to try next. i bet money it does nothing. going on 3 months this truck has been down. i just can't wrap my head around it. the computer says it is dosing DEF at 10-13% at times but the level never goes down in the tank, but you do the dosing tests and the DEF doser sprays fine. just don't get it. I am almost wondering if there is some kind of electrical interference when the engine is running. dosing tests are done when it is not running and it works fine. I bet/hope Mack will send engineers out on this one. NOBODY can figure it out.

put in used ACM today and did 4 regens, same issue. says it's dosing 10-15% and tank level never goes down. 4094 fmi 1 still active. ordered a new DEF pump now. i was reading in tech tool and it said the ACM sends signal to the DEF pump and the internal electronics of the pump deciphers and adjusts dosing amount accordingly. doesn't make sense to me that it works on all the tests but not in normal operation. not all repairs make sense i guess. just throwing parts at it since i don't know what else to do.

we know the problem is the DEF doser is not dosing and that's why the NOx is high. you do the Doser tests in tech tool and it is dosing fine in test mode. so we know the pump, lines, doser are good because they work in test mode. in normal operation, it says it is dosing at 10% or whatever but the tank level never changes. we are waiting for a used ACM out of another truck right now.

we took it to Mack they replaced the EGR cooler and EGR diff sensor and Venturi tube with new. they said it needed injectors. we replaced the injector and still the same problem. we have now replaced the ACM but Mack programmed the new one with the old ones program. it still id not dosing unless your in test mode, then it doses fine. 4094 will not go away, it is still not dosing. we are trying to get a used ACM from a good working truck.

ANYONE? the truck says it's dosing at 10% during a regen but the tank level never goes down. new inlet NOx sensor and still nothing. doses fine on all the test modes but it isnt dosing normally. need help!

I have a 2012 Mack with MP7. have codes SPN4094 FMI 1&18. SPN 5246 FMI 0, 15, 16. Code 4094 FMI 1 is the only one active now. i have seen past threads on this. 13PSI boost, temps all good, around 900. DPS .13 I have done many regens. new outlet NOx sensor and DEF doser. . DPF not passing soot. Decomp tube completely clean and clear. NOx drops down to around below 100 then comes back up to 200 after regen. the DEF doser says its dosing but the tank level never goes down during the regen it said is was dosing 10% but NOx stayed at 510. i have done all the dosing tests they all pass and the doser is spraying fluid out and amount seems correct (when testing the tank level goes down.). Truck is hard starting and probably needs injectors and cups but it has been that way all summer and not had SCR codes. after regen NOx is steady at 230. rev to 1500 and it goes down to 100. then idle it dips to 90 but then back up to 230 DEF dosing valve percentage stays at 0 after the regen.

old atomization module had number on it of 1578198X 2258875 new one number are 1578195X and 22258878 electrical connector is different. updated module? do I have the correct one? Truck:2012 MACK MRU613 VIN:1M2AV02CXCM008726

So we got a truck from another site. 2012 MRU spark assist DPF. It won't regen. There is one code for Atomization air mechanical system not responding. SPN3485 FMI 7. replaced the pressure sensors on the atomization module. still same code. replaced the atomization module with new. same code. have good air pressure going to the module. turn the air valves on and off with the computer. hearing click and hear and feel air out the tube going to the fuel nozzle. when truck starts to regen see 36 psi of so on the computer for atomization air. it clicks the shutoff and the psi goes to 0. I went through the troubleshooting and it says something about when you manually turn the atomization air shutoff on the air pressure should be less than 17psi. i did it and it shows 36psi it says to replace the atomization module, but we already did. same problem with either module. the computer says the air is internally regulated in the Atomization module. does it need to be before the module? Please help i'm stumped.

I thought I would type an update to this. The dealer replaced the Turbo and the EGR valve and cooler and that seemed to fix it. I believe it was the turbo because we checked the EGR valve and the cooler and they were fine. Just odd that it would only do it in regen. but its been running great since. knock on wood.!! Thanks everyone

this truck had a fuel pressure regulator code when this all started. my boss said there is some Mack bulletin https://static.nhtsa.gov/odi/tsbs/2021/MC-10189885-0001.pdf

We have a 2018 MACK LR613 MP7 with code P2A1F Injection Pump Fuel Metering Control "f" Range Performance. it sets at random times during route. when the code sets the engine is de-rated until we clear the code. the truck went to the dealer twice for this problem. 1st time they replaced injectors and the injector harness. the did the fuel pressure regulator delete upgrade. came back, first day it acted up again. went back to the dealer. they said all they did was check the wiring and injectors. came back and ran 3 weeks with no issue. now the code is setting everyday same problem. Any thoughts?

where is the EGR test in PTT? we did the intake and exhaust check test and the EGR flow stays at 0. while we had that test going we hit regen and EGR flow still said 0. how or when should we see EGR flow? only while driving?

but only when we put it in regen

So with the DPF/DOC off there is little to no smoke unless you snap the throttle hard. we hit the regen button and then it starts pouring the smoke out. so whatever is causing it, it only happens when the truck is trying to regen. we unhooked the DRV put it in regen and it starting pouring smoke out. we plugged off the 7th injector fuel line and same thing, pouring smoke out.

we took the DRV off and checked it. it opens and closes with air pressure.