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HFT Control Unit Input Test/Replacement

  1. Disconnect the 28P connector (A) from the Hands Free Telephone control unit (B).
  1. Inspect the connector and socket terminals for a good pinfit to be sure they are all making good contact.
    • If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
    • If the terminals look OK, go to Step 4 .
  1. Reconnect the connector and make these input tests at the connector.
    • If any test indicates a problem, find and correct the cause, then recheck the system.
    • If all the input tests prove OK, go to Step 5 .
    Cavity
    Wire
    Test condition
    Test: Desired result
    Possible cause if desired result is not obtained
    1
    BLK
    Under all conditions
    Check for voltage to ground: There should be less than 0.5 V.
    • Poor ground (G602)
    • An open in the wire
    15
    PNK
    Under all conditions
    Check for voltage to ground: There should be battery voltage.
    • Blown No. 1 (10 A) fuse in the under-hood fuse/relay box
    • An open in the wire
    16
    PUR
    Ignition switch ON (II)
    Check for voltage to ground: There should be battery voltage.
    • Blown No. 14 (7.5 A) fuse in the under-dash fuse/relay box
    • An open in the wire

  1. Disconnect the 28P connector again, and make this input test at the connector.
    • If the test indicates a problem, find and correct the cause, then recheck the system.
    • If the input test proves OK, the Hands Free Telephone control unit must be faulty, replace it.
    Cavity
    Wire
    Test condition
    Test: Desired result
    Possible cause if desired result is not obtained
    18
    LT GRN
    Under all conditions
    Check for continuity between No. 18 terminal and the driver's under-dash fuse/relay box connector Q (16P) terminal No. 3: There should be continuity.
    An open in the wire
    Driver's under-dash fuse/relay box connector Q (16P) disconnected
    Check for continuity to ground: There should be no continuity.
    Short to ground