Another Code: P0174

Discussion in 'SRT Hellcat Maintenance' started by SRT HC, Aug 11, 2015.

  1. SRT HC

    SRT HC BANNED

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    In addition to the P2629 CEL I got Monday morning, this evening (Tuesday) I got code P0174 when I started the car.
    It seemed to surge in Drive at the first red light I came to. I put in Neutral and seemed okay. I thought I felt a very slight surging while driving the four or five miles home.

    Any ideas?
     
  2. fnkychkn

    fnkychkn swollen member Gold Supporting Member

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    You'll want to get the P2629 fault taken care of first.

    From FSM:

    P0174-FUEL SYSTEM 2/1 LEAN

    Theory of Operation

    The intent of this diagnostic is to identify rich or lean fuel system abnormalities which would cause vehicle emissions to exceed 1.5 times any of the standards. This is accomplished by monitoring the Short Term and Long Term fuel trims. If they exceed a calibrated threshold for a calibrated time, a fuel system problem is occurring. This feature is active under all closed loop fuel conditions.

    Since the Downstream O2 Sensor is after the catalyst, it is protected from chemical poisons (like silicon and phosphorous) and protected from thermal aging. The Downstream O2 Sensor feedback optimizes the catalyst efficiency and normalizes the tailpipe emissions based on the Downstream O2 Sensor output, especially when the system components are no longer at nominal values. The Powertrain Control Module (PCM) monitors the Downstream O2 Sensor feedback control, called downstream fuel trim, to detect any shift in the Upstream O2 Sensor target voltage from nominal target voltage.

    Upstream and Downstream fuel trim monitors operate very differently. The Upstream O2 Sensor can adjust the goal voltage to accommodate for slight fuel/air variances. The Downstream O2 Sensor has a fixed goal voltage to maintain catalyst efficiency.

    The upstream fuel trim diagnostic is designed to detect a large change (33% from nominal) and will generally fail quickly. The downstream fuel trim diagnostic is designed to catch small failures (from worn components) over a longer period and therefore takes much longer to fail. The possible causes for both diagnostics are the same but the upstream is detecting a gross failure condition and the downstream will detect a smaller, less obvious condition.


    When Monitored and Set Conditions

    When Monitored: This diagnostic runs continuously when the following conditions are met:

    Engine running in closed loop mode. Ambient/Battery temperature above -6.7°C (20°F). Altitude below 2590.8 m (8500 ft).

    Set Conditions:

    When the Powertrain Control Module (PCM) multiplies short term compensation by long term adaptive and a certain percentage is exceeded.

    Default Actions:

    The MIL light will illuminate.


    Possible Causes
    RESTRICTED FUEL SUPPLY LINE
    FUEL PUMP INLET STRAINER PLUGGED
    FUEL PUMP MODULE
    O2 SIGNAL CIRCUIT
    O2 RETURN CIRCUIT
    O2 SENSOR
    MAP SENSOR
    ECT SENSOR
    ENGINE MECHANICAL
    FUEL FILTER/PRESSURE REGULATOR
    POWERTRAIN CONTROL MODULE (PCM)
     
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  3. Snappycat

    Snappycat SRT Hellcat Moderator Staff Member

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    Chkn...very useful info. Your tech posts benefit us all....if not now...perhaps in the future. Thanks for sharing:)
     

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