AFM not responding during tech tool test command

Discussion in 'Mack Forum' started by devedo, Mar 7, 2019.

  1. devedo

    devedo Light Load Member

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    Have a 2013 Mack CXU that is having some SCR efficiency issues, but while doing the tests discovered a communication issue as well.

    AFM does not respond to any tests other than regen requests or scr crystalization sublimination test. No faults in system other than the scr efficiency fault which is now inactive after the scr was cleaned.

    Can monitor all the afm sensor readings and when the afm is unplugged the usual j1939 faults come active for an open circuit.

    Have cleaned ecm, afm, and firewall conncections.

    The afm module does not show up on Tech Tool monitoring either. Dont know if is supposed to or not. Only have been using the software for a day. Used a generic program before purchasing Tech tool.

    Anybody ran into this before? 20190307_141307.jpg 20190307_141348.jpg
     
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  3. devedo

    devedo Light Load Member

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    Also the customer did take it to a mack dealer for this scr issue and they swapped the afm with a test module, but still had the same results.
     
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  4. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    First, not to be picky, it is called an acm not afm. Only say this because it helps while reading your comments. The acm has to be recognized in order to do any troubleshooting. Did I read correctly that you are able to complete a forced regen and/or an scr sublimination test with no issues?
     
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  5. devedo

    devedo Light Load Member

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    Yes I can complete a regen and an scr sublimination test without issues. It will set faults for any of the after treatment sensors being unplugged, was throwing the scr efficiency fault, and requests parked regents when needed with this communication issue.

    Since I posted this I've checked and cleaned the module connectors, batteries, and firewall connectors. Also tested both data networks. Disconnected the elog system from the data network, but did not change the issue.
     
  6. devedo

    devedo Light Load Member

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    I was calling it the wrong acronym. I work on everything, not just macks/volvos and I do mix up the acronyms often. My mistake. And yes it does help to call them by the correct one
     
  7. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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    The acm receives its 12v+ from the wire in the battery box that is fuse protected. Pop the cap off and check that fuse and also the connection to the battery post. I am sure that it will be a re check for you after seeing what you posted. Next go to acm connector and unplug it. Use a razor and cut the tape about 6" or so to expose the wiring. You will see a particular gray wire that transforms from 3 wires into 1 wire protected by black heat shrink. This is your 12v+ for acm. I have found that the connection inside the heat shrink goes bad. Lastly, check that whole harness, especially on both sides of the square connectors. Open the tape with a razor. Have done 3 repairs just this week because of all the snow/ice/rain/salt.
     
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  8. GreenLightTransportation

    GreenLightTransportation Bobtail Member

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    QUALITYTRUCK, your post saved me a whole lot of time and money. The batteries were replaced on my CXU613 and right after, the entire emission wasn't functioning. The ACM fuse was only getting around 4 volts. Because of your advise, I simply moved around the ACM wire, made a better connection and the ACM got the power it needed.

    2 years later and your post really saved me. Thank you!

    Check to see how much voltage is passing thru the ACM fuse if you're getting this code. If it's less than 12V, clean up the wire, make a better connection and see if that solves the problem.

    Thanks QUALITYTRUCK
     
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  9. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

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