Test Procedure

2009 Mercury Milan Premier, 3.0 1, AWDSECTION Test Procedure
WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
  1. TD1 DIAGNOSTIC TROUBLE CODE (DTC) P0A18: VERIFY THAT THE CONCERN IS PRESENT 
    • Record and clear all continuous memory DTCs.
    • Retrieve the PCM continuous memory DTCs.

    Is DTC P0A18 present? 

    Yes No
    GO to  TD2. GO to  TD7.
  2. TD2 CHECK THE TMAC CIRCUIT FOR AN OPEN CIRCUIT IN THE HARNESS 
    • Ignition OFF.
    • PCM connector disconnected.
    • Transaxle Assembly-B connector disconnected.
    • Measure the resistance between:
      (+) PCM Connector, Harness Side (-) Transaxle Assembly-B Connector, Harness Side
      TMAC - Pin C6 TMAC - Pin 4

    Is the resistance less than 5 ohms? 

    Yes No
    GO to  TD3. REPAIR the circuit.
    CLEAR the DTCs. REPEAT the self-test.
  3. TD3 CHECK THE TMAC CIRCUIT FOR A SHORT TO VOLTAGE IN THE HARNESS 
    • Ignition ON, engine OFF.
    • Measure the voltage between:
      (+) PCM Connector, Harness Side (-) Vehicle Battery
      TMAC - Pin C6 Negative terminal

    Is the voltage less than 1 V? 

    Yes No
    GO to  TD4. REPAIR the circuit.
    CLEAR the DTCs. REPEAT the self-test.
  4. TD4 CHECK THE TMAC CIRCUIT FOR A SHORT TO GROUND IN THE HARNESS 
    • Ignition OFF.
    • Measure the resistance between:
      (+) PCM Connector, Harness Side (-) Vehicle Battery
      TMAC - Pin C6 Negative terminal

    Is the resistance greater than 10K ohms? 

    Yes No
    GO to  TD5. REPAIR the circuit.
    CLEAR the DTCs. REPEAT the self-test.
  5. TD5 CHECK FOR THE TMAC CIRCUIT SHORTED TO SIGNALS IN THE SAME HARNESS 
    • Measure the resistance between:
      (+) Transaxle Assembly-B Connector, Harness Side (-) Transaxle Assembly-B Connector, Harness Side
      TMAC - Pin 4 ISDN2 - Pin 7
      TMAC - Pin 4 GSDN - Pin 10
      TMAC - Pin 4 CTO - Pin 1
      TMAC - Pin 4 TGAC - Pin 9
      TMAC - Pin 4 MSDN - Pin 5

    Are the resistances greater than 10K ohms? 

    Yes No
    GO to  TD6. REPAIR the circuit.
    CLEAR the DTCs. REPEAT the self-test.
  6. TD6 TMAC FUNCTIONAL TEST 
    • PCM connector connected.
    • Transaxle Assembly-B connector connected.
    • Isolate the TMAC pin from the Transaxle-B connector.
    • Connect a 5 amp fused jumper wire between the following:
      Point A Transaxle Assembly-B Connector, Harness Side Point B Transaxle Assembly-B Connector, Harness Side
      TMAC - Pin 4 TGAC - Pin 9
    • Ignition ON, engine running.

    Does the engine start now? 

    Yes No
    INSTALL a new transaxle assembly. REFER to the AUTOMATIC TRANSAXLE/TRANSMISSION - 6F35 . GO to  TD8.
  7. TD7 CHECK THE TMAC CIRCUIT FOR AN INTERMITTENT CONCERN 
    • Ignition ON, engine OFF.
    • Access the PCM and monitor the MTQ PID.
    • Carefully wiggle all accessible wiring and connectors associated with the circuit and look for a change in the PID state.

    Is a concern present during the wiggle test? 

    Yes No
    REPAIR as necessary.
    CLEAR the DTCs. REPEAT the self-test.
    GO to PINPOINT TEST Z .
  8. TD8 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Visually inspect for:
      • pushed out pins
      • corrosion
    • Connect all the PCM connectors and make sure they seat correctly.
    • Carry out the PCM self-test and verify the concern is still present.

    Is the concern still present? 

    Yes No
    INSTALL a new PCM.
    REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) .
    The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.