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Pinpoint Test L: The THX® Amplifier Does Not Respond To The Scan Tool

WARNING: This page is about a different car, the 2007 Lincoln MKX and 2007 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. L1 CHECK THE THX® AMPLIFIER VOLTAGE SUPPLY CIRCUITS FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: THX® Amplifier C4348c
    • Key in ON position.
    • Measure the voltage between the THX® amplifier, harness side and ground as follows:
      Connector-Pin Circuit
      C4348c-9 SBP38 (BN/RD)
      C4348c-10 SBP38 (BN/RD)
      C4348c-11 SBP18 (YE/RD)
      C4348c-12 SBP18 (YE/RD)
    • Are the voltages greater than 10 volts? 
    1. YES  : Go to  L2.
    2. NO  : VERIFY the smart junction box (SJB) fuse 38 (20A) or fuse 18 (20A) is OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
  2. L2 CHECK THE THX® AMPLIFIER GROUND CIRCUITS FOR AN OPEN 
    • Key in OFF position.
    • Measure the resistance between the THX® amplifier, harness side and ground as follows:
      Connector-Pin Circuit
      C4348c-22 GD148 (BK/YE)
      C4348c-23 GD148 (BK/YE)
      C4348c-24 GD148 (BK/YE)
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  L3.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
  3. L3 CHECK THE MS-CAN CIRCUITS BETWEEN THE DATA LINK CONNECTOR (DLC) AND THE THX® AMPLIFIER FOR AN OPEN 
    • Disconnect: THX® Amplifier C4348a
      • Fig 1: Measuring Resistance Between THX® Amplifier C4348A-11, Circuit VDB06 (GY/OG) & DLC C251-3
      GF0023545Courtesy of FORD MOTOR CO.
    • Measure the resistance between the THX® amplifier C4348a-11, circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.
      • Fig 2: Measuring Resistance Between THX® Amplifier C4348A-12, Circuit VDB07 (VT/OG) & DLC C251-11
      GF0023546Courtesy of FORD MOTOR CO.
    • Measure the resistance between the THX® amplifier C4348a-12, circuit VDB07 (VT/OG), harness side and the DLC C251-11, circuit VDB07 (VT/OG), harness side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  L4.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
  4. L4 CHECK FOR CORRECT THX® AMPLIFIER OPERATION 
    • Disconnect all the THX® amplifier connectors.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect all the THX® amplifier connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a THX® amplifier. REFER to INFORMATION AND ENTERTAINMENT SYSTEMS . CLEAR the DTCs. REPEAT the network test with the scan tool.
    2. 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 network test with the scan tool.
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