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Test B: Front Radio Control Unit Does Not Respond To NGS Tester

WARNING: This page is about a different car, the 1999 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Front radio control unit may also be referred to as Audio Control Module (ACM).
  1. Turn ignition switch to LOCK position. Disconnect front radio control unit 20-pin harness connector C258 located behind center of instrument panel, on radio. See Figure. Inspect harness connector for loose, damaged or corroded terminals. Repair as necessary and retest system for normal operation. If harness connector is okay, reconnect harness connector C258. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If NGS tester indicates FCM: NO RESPONSE ON CKT 914 (BUS +), go to next step. If NGS tester does not indicate FCM: NO RESPONSE ON CKT 914 (BUS +), go to step  3.
  2. Turn ignition switch to LOCK position. Disconnect NGS tester. Disconnect front radio control unit 20-pin harness connector C258. Measure resistance in Tan/Orange wire between terminal No. 3 at front radio control unit harness connector C258 and terminal No. 2 at Data Link Connector (DLC). See Figure and Fig 1 . If resistance is less than 5 ohms, replace front radio control unit and retest system for normal operation. If resistance is 5 ohms or greater, repair open Tan/Orange wire between front radio control unit harness connector and DLC. Retest system for normal operation.
  3. Turn ignition switch to LOCK position. Disconnect NGS tester. Disconnect front radio control unit 20-pin harness connector C258. Measure resistance in Pink/Light Blue wire between terminal No. 4 at front radio control unit harness connector C258 and terminal No. 10 at DLC. See Figure and Fig 1 . If resistance is less than 5 ohms, replace front radio control unit and retest system for normal operation. If resistance is 5 ohms or more, repair open in Pink/Light Blue wire between front radio control unit harness connector and DLC.
Fig 1: Identifying Front Radio Control Unit Harness Connector C258 Terminals
G98D01713Courtesy of FORD MOTOR CO.
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