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Pinpoint Test U: Dual Generator Lower Fault Detected (P1148)

WARNING: This page is about a different car, the 2005 Ford Pickup, 2005 Ford F550 Super Duty, 2005 Ford F450 Super Duty, and 2005 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
  1. U1 CHECK THE LOWER GENERATOR CONNECTIONS 
    • Key in OFF position.
    • Disconnect: Lower Generator C1251c, C1251a.
    • Check the lower generator connectors for damage and correct connection.
    • Connect: Lower Generator C1251c, C1251a.
    • Are the lower generator connectors OK and correctly connected? 
    • Yes  : GO to U2.
    • No  : REPAIR the connectors as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  2. U2 CHECK THE LOWER GENERATOR B+ VOLTAGE 
    • Measure the voltage between the B+ terminal of the lower generator and ground.
      Fig 1: Measuring Voltage Between B+ Terminal Of Lower Generator And Ground
      G03924859Courtesy of FORD MOTOR CO.
    • Is the voltage equal to battery voltage? 
    • Yes  : GO to U3.
    • No  : CHECK the B+ circuit 36 (YE/WH) including the fusible links. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  3. U3 CHECK THE LOWER GENERATOR A CIRCUIT 
    • Disconnect: Lower Generator C1251a.
    • Measure the voltage between the lower generator C1251a pin 3, A circuit 35 (OG/LB), harness side and ground.
      Fig 2: Measuring Voltage Between Harness Connector And Ground
      G03890319Courtesy of FORD MOTOR CO.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to U4.
    • No  : CHECK the lower generator A circuit 35 (OG/LB) including the fusible links. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  4. U4 CHECK THE LOWER GENERATOR I CIRCUIT VOLTAGE 
    • Key in ON position.
      • NOTE: Wait at least 2 minutes for the glow plugs to stop cycling.
      Fig 3: Measuring Voltage Between Connector And Ground
      G03890314Courtesy of FORD MOTOR CO.
    • With the key ON, engine OFF, measure the voltage between the lower generator C1251a pin 1, circuit 1185 (YE), harness side and ground.
    • Is the voltage greater than 10 volts? 
    • Yes  : GO to  U6.
    • No  : GO to U5.
  5. U5 CHECK THE LOWER GENERATOR I CIRCUIT FOR AN OPEN OR A SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: PCM C1381c.
    • Key in ON position.
    • With the key ON and the lower generator C1251a disconnected, measure the resistance between the lower generator C1251a pin 1, I circuit 1185 (YE), harness side and the PCM C1381c pin 4, circuit 1185 (YE), harness side; and between the lower generator C1251a pin 1, I circuit 1185 (YE) harness side and ground.
      Fig 4: Checking Lower Generator I Circuit For Open Or Short To Ground
      G03924877Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms between the generator and the PCM, and greater than 10,000 ohms between the generator and ground? 
    • Yes  : GO to  U8.
    • No  : REPAIR the I circuit 1185 (YE). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  6. U6 CHECK THE LOWER GENERATOR VOLTAGE 
    • Connect: PCM C1381c.
    • Disconnect: Upper Generator C102a.
    • Connect: Lower Generator C1251a.
    • Key in START position.
      • NOTE: After starting the engine, wait at least 2 minutes for the glow plugs to stop cycling.
      Fig 5: Measuring Battery Voltage
      G03879700Courtesy of FORD MOTOR CO.
    • With the engine running, measure the voltage at the battery.
    • Is the voltage greater than 13 volts? 
    • Yes  : GO to U7.
    • No  : INSTALL a new lower generator. REFER to GENERATOR AND REGULATOR . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  7. U7 CHECK THE LOWER GENERATOR OUTPUT 
    • Yes  : The system is operating normally. CONNECT all the connectors. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
    • No  : INSTALL a new lower generator. REFER to GENERATOR AND REGULATOR . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  8. U8 CHECK FOR CORRECT PCM OPERATION 
    • Disconnect all the PCM connectors.
    • Check for:
      • corrosion
      • pushed-out pins
    • Connect all the PCM connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    • Yes  : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS - DIESEL ENGINE . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
    • No  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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