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Pinpoint Test G: No Communication With The 4WD Module (Pcm)

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multimeter probes.
  1. G1 CHECK CAN COMMUNICATION 
    NOTE: To distinguish between a loss of CAN communication to the 4WD module and a loss of CAN communication with the entire vehicle, the ABS module CAN communication is verified because it uses CAN for diagnostics.
    • Verify CAN communication with the anti-lock brake system (ABS) module.
      • If using the WDS, follow the directions and carry out the network test.
      • If using VCM, verify that the vehicle and engine selection information are correct.
    • Does the diagnostic tool communicate with the ABS module? 
    • Yes  : GO to G2.
    • No  : REFER to the appropriate diagnostic tool manual for further diagnosis.
  2. G2 CHECK THE FUSES 
    • Check BJB fuse 18 (20A) and CJB fuse 24 (15A).
    • Are the fuses okay? 
    • Yes  : GO to G3.
    • No  : REPAIR as necessary. REPEAT the self test.
  3. G3 CHECK FOR BATTERY VOLTAGE FROM THE BATTERY JUNCTION BOX (BJB) 
    • Key in ON position.
    • Measure the voltage between BJB input side fuse cavity 15 and ground; measure the voltage between BJB input side fuse cavity 20 and ground.
    • Are the voltages greater than 9 volts? 
    • Yes  : GO to G4.
    • No  : REPAIR or INSTALL new components as necessary. REPEAT the self test.
  4. G4 CHECK FOR VOLTAGE INPUT TO THE 4WD MODULE (PCM) 
    • Disconnect: 4WD Control Module (PCM) C175b.
    • Key in ON position.
    • Measure the voltage between 4WD module 175b-49, circuit 729 (RD/WH), harness side and ground; measure the voltage between 4WD module 175b-50 circuit 994 (WH) harness side and ground.
    • Are the voltages greater than 9 volts? 
    • Yes  : GO to G5.
    • No  : REPAIR the affected circuit(s). REPEAT the self test.
  5. G5 CHECK THE GROUND CIRCUITS FOR AN OPEN 
    • Measure the resistance between C175b-47, circuits 570a C175b-48, circuit 570b C175b-49, circuits 570c, (BK/WH) and ground.
    • Are the resistances less than 5 ohms? 
    • Yes  : GO to G6.
    • No  : REPAIR the affected circuit(s). REPEAT the self test.
  6. G6 CHECK THE BATTERY VOLTAGE WITH THE ENGINE RUNNING 
    • Start the engine.
    • Measure the battery voltage at the positive battery terminal.
    • Is the voltage greater than 9 volts? 
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