eml light with code P20E8

Discussion in 'Engine' started by dannyfiveforty, Aug 14, 2017.

  1. dannyfiveforty

    dannyfiveforty New Member

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    Sep 2, 2008
    Good evening,

    Yesterday morning my eml came on, I read the code P20E8 "reductant pressure too low" the car seemed to be running as normal, I erased the code but then it came back again this morning.

    Has anyone any experience with this code or have any suggestions I can try to diagnose before I have to book it in to the dealer.

    Many thanks
     
  2. Codger49

    Codger49 Hardcore MB Enthusiast

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  3. OP
    OP
    dannyfiveforty

    dannyfiveforty New Member

    Messages:
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    Sep 2, 2008
    Thanks for the link. Sorry I thought it was in my signature. It is a 2011 s350 bluetec. Thanks
     
  4. Tuercas viejas

    Tuercas viejas Hardcore MB Enthusiast

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    landrover/rolls royce/MB AMG S600/Prius
    The fault requires a full interrogation of the system using a factory style scanner.

    There are factory prescribed tests following scanner prompts which check actual pump delivery pressure and return which is in the region of 5000 HPa.

    There is also a practical test which requires the dosing injector to be removed from the exhaust system at what I call the "bazooka tube" and record its actual delivery quantity, again measured in ML with the injector dangling into a burette over a set period depending upon the model on test
    .
    As a quick DIY inspection you could check the wire harness going to the injector for detachment or burning against the "zorst pipe" and check the DEF fluid connector for leakage . Equally you can also remove the band clamp holding the dosing valve to the bazooka tube & withdraw it.
    Check the nozzle for crusting of DEF deposits which can corrupt the three prong injection spurts that diffuse themselves as an atomised fluid stream into the exhaust gas flow when operating.
    All parts have to be SCN encoded when changing them out especially the pump or heater elements in the tank module. So again a factory style scanner is essential to fix it right first time.
    At the same time I/We also check the NOx sensor for operation after the repair to make sure they are seeing a minimum of 75% NOx reduction in the Cat "bazooka tube" & out the tail pipe .
    All the best & good luck.
    Tuercas Viejas
     

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