Mass Air Flow/Vane Air Flow Sensor Circuit Above Maximum Voltage (O,M,R) Causing CEL

Discussion in '94-95 5.0 - Specific' started by Rob95DFW, Mar 16, 2014.

  1. Rob95DFW

    Rob95DFW New Member

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    Hello,

    I have a 1995 Mustang GT with the following mods:

    E Cam
    Longtubes
    Mac Prochamber
    SLP Dumps
    CAI
    C&L 76mm MAF (Calibrated for 19lb Injectors)
    No Smog Pump
    All EGR is in place and hooked up

    Everything else is stock. However, I am getting a 56 - Mass Air Flow/Vane Air Flow Sensor Circuit Above Maximum Voltage (O,M,R) code and I don't know what I need to do to get it resolved.

    I have cleaned the MAF, replaced IAC (AutoZone part), replaced all vacuum lines, replaced EGR gasket and cleaned it, replaced TB/Upper Intake Manifold gasket.

    When I replaced the IAC, the car began to have a hang idle issue as well. When I shift gears, the idle increseases 300 - 400 RPM and then will fall down. When I come to a complete stop the car will idle about 1100 RPM and eventually fall down.

    I don't know what else to do with this. If I run the car, the CEL will illuminate, but if I turn the car off and re-start it, the CEl is off for a few minutes and then comes back on.

    Any help would be appreciated!

    Robert
    1995 Mustang GT 5.0
     
  2. ttocs

    ttocs Legend

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    I would try replacing the maf and see if it clears it up. Double check the wiring going to it so ensure there is no bare copper showing or loose wires.
     
  3. Addermk2

    Addermk2 Well-Known Member

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    [​IMG]

    Disconnect the main ECU harness and the maf harness plugs. Check continuity at each end of pins 9 and 50. While both ends are disconnected, turn the key on, and look for voltage on pins 9 and 50. Also check the voltage on the red wire in the MAF harness.

    Assuming your car does not have a tune. The 56 code you are getting it set by the ECM triggering PID VMAMAX. Basically either pins 9 or 50 are seeing more than 4.9vdc at a given time.
     
  4. Rob95DFW

    Rob95DFW New Member

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    If they are getting more than 4.9 how do you fix that?
     
  5. toyman

    toyman Active Member

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    How can a '95 get a 2 digit code (56)? They are all 3 digits. MAF codes for the '94-'95 are 157, 158 and 159.
     
  6. Addermk2

    Addermk2 Well-Known Member

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