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Our automotive experts have put together the following information about the P20A4 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P20A4 code.

OBD II Fault Code

  • OBD II P20A4

    OBD-II Code Powertrain Control Module (PCM) failure is defined as a Reductant Purge Control Valve Stuck Open

    Diesel Exhaust Fluid (DEF) is used to assist in converting leftover exhaust particles to harmless gases. In order to burn off those particles, the temperature of the exhaust system needs to increase. the injection of DEF Fluid into the exhaust stream brings Diesel Particulate Filter (DPF) up to temperature. The system is then able to convert harmful NOx to Nitrogen, Carbon Dioxide, and water. The Reductant Catalyst (SRC) was added to further reduce any NOx was still in the exhaust stream. The Reductant Purge Valve controls the flow of DEF (Diesel Exhaust Fluid) from the pump to the injector. If the Reductant Purge Valve does not operate as requested by the engine computer, code P20A4 will set.

    Powertrain Control Module (PCM) failure Symptoms

    • DPF regeneration may not occur

    Common Problems That Trigger the P20A4 Code

    • Powertrain Control Module (PCM) failure
    • Reductant purge valve failure
    • Wiring issue
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