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2009-2010 mack cxu m7 any typical major problems?


daniel24lee
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we have a fleet of 20 road trucks that are all mack 2008-2010 cxu and 5 are new 2014 chu's... I am having a heep of problems with the 09 cxu's from a goast in the wiring I assume, to one that wont even start even with starting fluid (yeah I know not good to do), hella problems with egr, dpf, p.o.s. not regening on there own and some that don't even really like to be forced to regen I have the tech tool program for these trucks (but never been shown how to really use it) teaching myself and I think im getting by, im the lead mechanic and have 10+ years exp. with diesel mechanic's but this new erg crap has got me pullin my hair out and throwing a lot of tools..... any help with common problems with thses trucks would help or if you even have a question about one specific truck please let me know I can give you more info

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Any codes will be very helpful. I'm not the best but iv been learning my self on the tech tool. Idk if messed with guided diagnostics any but it's very helpful. Challenger and staxx always help me out on here there really good so any problems you have just post and some one will be able help you out.

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Plugged EGR diff pressure sensor tubes. These are the tubes near the intake manifold. The tubes and/or ports clog. Causes low power

Cracked flex pipes. This is the flex pipe before the DPF. Causes excessive regens.

Plugged 7th injectors. This is the injector after the turbo. Cause incomplete or excessive regens.

Post problem/complaint and codes up front for quicker replies.

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ok I have one going into mack dealer for im going to say wiring issues (herein referred to as truck 120) its a 2009 mack cxu613 pinnacle mp7... the only codes are mid 128-pid 411-fmi 5; gas diff pressure like challenger said, I tested the wiring unplugged from sensor and I get with key on, one ground, one 4.99 volt, and one 4.75 volt (on signal wire).... 0nly other code is; mid 128-pid 437-fmi 5; aftertreatment injector fuel pressure sensor and get the same reading when I test the wiring one ground one 4.99 and one 4.55..... now the main problem we r having is it goes into shut down mode and even sometimes dies going down the road or at best wont rev up pass 1200 rpm's. yes it will not regen on its own because of the sensor codes.... but I have messed with it and just idling in the yard I set the high idle at 1000 rpm's and the cruise some times will kick out and then by foot you cant rev it up pass 1200 rpm's, so I held the peddle to the floor and 1200 was it no more turned the cruise on/off switch off and it jumped to 2200.... so I did the same thing over 2-3 more times and same out come soon as I turned the cruise off it jumps to 2200.... so I take the cruise switch out and send it to work it runs ok for a couple days then same thing happens but now its in the atc circuit atc light on dash comes on by its self and kills the truck. I had him shut the truck off at the key and wait 20 seconds and start it back up and it runs good for 50 miles then atc light and power reduction...... I have reprogramed the ecm and updated it also.each time it gets to the yard says the soot level is 50-75% never more then 75% ive done force regen and it goes down but don't help the main problem. now to my credit I just got my tech tool working right I had to delete the program off my computer twice and reinstall it but its finally working OK still not good but ok but I just found the 2 codes yesterday and while testing the wiring at the sensor the codes went inactive....wiring?....now the truck has no active codes and still same thing with cruise on wont get over 1200 rpm's

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ok Kyle, the one that wont fire on fluid (herein referred to as truck 119 yes sister truck to 120 vin numbers are different only by the last number a 2 and a 5)...it has a lot of codes so Im not gunna type the meaning of them all but here they are...; mid 136-sid 3-fmi 7.....mid 128 pid 153 fmi 0..... mid 128 pid 153 fmi 2..... mid 128 pid 153 fmi 3.... mid 128 sid 39 fmi 0 mid 140 pid 177 fmi 5.....mid 144 pid 84 fmi 2..... mid 144 pid 84 fmi 5..... mid 144 pid 91 fmi 13.... now 2 of the codes I have fixed one is the accelerator peddle and the info display gear box oil and it still don't even try to start..... and we are in the oil field also nut in Wyoming and its been cold cold up here.. that reminds me before 119 stopped running its always been hard to start in the mornings while its in the negitives and even this last time at 20 above..... just a guess but im thinking its the copper cones in the heads that seat the injectors..... im going to run the diagnose program and some other tests today on it since I just figured it out last night on truck 120 I will post anything else I find....... thanks for the replies and help fella's

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Not that I'm much help here, but your cruise control/high idle and only 1200 revs is something my 2011 mp7 granite does too. After it's run a few mins in the morning (while kicking the tires and checking lights), I'll turn the idle up to about 1000 to warm it up. If I push the yellow button in or touch the brake pedal or clutch pedal, the idle drops back to low (650-700) and it'll rev on the throttle but only to 1400.... If I flip the cruise switch off while on the throttle it revs like it's supposed to. Just putting that out there.

Lack of planning on your part does not constitute an emergency on my part....

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Ok I found threw googling problems ( also how I found this site). Type in Mack 2010 emissions manual, the first one on the list should be threw aurora Mack. It is a very helpful guide for these emission codes. It'll tell you what conditions set each code and possible causes. I printed it out and uses it almost daily.

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Yep sound to be a very likely culprit. As for checking the injector cups challenger learned me a couple weeks ago the best way is to run a clear line from the rear of fuel filter housing to the rear of the head and from the overflow one the front to the front of housing or tank and you will see air comein out if the head but not goin in hens compression into fuel galley. But bein as it won't run well have to wait his reply on that I haven't ran in to that yet. Iv only had 2 cup issues an there were low power burning coolant and the other just running like crap. There is also a bulletin icons on Google threw Bruckners Mack if you type in Mack air in fuel system check. Hope it goes well for you. I know how big of. Headache these things Can be.

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thanks J maybe that's just how its programed ill have to look and see. but none of the other trucks do this that's why I didn't think it was suppose to and also it does the same thing going down the road limits the power to 1200 rpm's........ Kyle thanks I will try the clear tube fuel check and see if I can fine anything out just cranking on it... I also checked the fuel and oil for signs of coolant and vice versa with nothing all was full and good .... also I printed the "book" out, thanks for the fyi.... also just to mention thses two trucks have under 400,000 miles (low 300's)

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Most of the time you will see a list of codes, there's always codes. Pick the major codes or high counts.

Truck 120 Since you're sending it to a dealer let them deal with it.

Truck 119

Hard start-excessive crank and over 300,000 miles I would also leans toward injector cups. The very cold weather could also make it hard to start too. We had temps below 0 here too, some trucks wouldnt start until we dragged them inside and let them sit. If its a strong sounding excessive crank I would think injector cups, lazy and slow crank would be cold weather.

Mid 128 Pid 153 is the crankcase pressure sensor, its on the valve cover. Crankcase and oil pressure sensors have been updated. Replace the sensor.

Mid 144 84 road speed sensor What trans is in the truck? Active? Inactive? how many times?

Mid 136 sid 3 fmi 7. I tackle these one at a time and only if its active or someone complains.

Mid 128 sid 39 fmi 0 no idea what this is.

You dont need to worry about every code, you need to figure out which ones to diagnosis.

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  • 6 years later...

Unplug the oil level sensor on the left side of the oil pan.. if oil is in the sensor side... you are "wicking" oil up to the EECU... the oil will be pulled to the EECU with the electrical path... It just carries it.... at  the EECU, Unplug the Harness' .. If you see oil in the plug and or sockets... It has "Wicked" oil.... this will cause a boatload of codes...   Oil by itself cant conduct electricity, but because there is fine metal dust in the oil due to engine wear, it now becomes conductive,,,,  Mack/Volvo made a short anti wicking harness for this... but I've done many engine harness replacements because of this... Then the codes are reduced or gone... Jojo

Edited by Joey Mack
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