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Test M: No Module/Network Communication - SCP Bus Link

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: Depending on module configuration, with all modules connected and with ignition switch in RUN position or with engine running 2-3 volts may be present at Data Link Connector (DLC) terminals No. 2 (Tan/Orange wire) and No. 10 (Pink/Light Blue wire). These are the Standard Corporate Protocol (SCP) diagnostic communications network circuits.
NOTE: Front radio control unit may also be referred to as Audio Control Module (ACM). Speed control servo may also be referred to as Next Generation Speed Control (NGSC) servo. Air Suspension/Electronic Variable Orifice (EVO) steering module may also be referred to as Rear Air Suspension Module (RASM). Instrument cluster may also be referred to as Hybrid Electronic Cluster (HEC).
  1. Inspect NGS tester connector for loose, damaged or corroded terminals. Repair connector as necessary and retest system for normal operation. If connector is okay, go to next step.
  2. Turn ignition switch to LOCK position. Inspect Data Link Connector (DLC) for physical damage, bent terminals or corrosion. Repair connector as necessary and retest system for normal operation. If connector is okay, go to next step.
  3. Turn ignition switch to LOCK position. Disconnect speed control servo 10-pin harness connector located in left rear of engine compartment. Measure resistance in Tan/Orange wire between terminal No. 1 at speed control servo harness connector and terminal No. 2 at DLC. See Figure and Figure . Also, measure resistance in Pink/Light Blue wire between terminal No. 2 at speed control servo harness connector and terminal No. 10 at DLC. If both resistance readings are less than 5 ohms, go to next step. If either resistance reading is 5 ohms or greater, repair open in Tan/Orange wire and/or Pink/Light Blue wire between harness connector C201 and DLC. Retest system for normal operation.
  4. Connect NGS tester. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle passed data link diagnostic test, except speed control servo, replace speed control servo and retest system for normal operation. If any module other than speed control servo did not pass data link diagnostic test, go to next step.
  5. Turn ignition switch to LOCK position. Disconnect 76-pin harness connector C201 located behind left side of instrument panel. See Figure. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except PCM, ABS module and speed control servo passed data link diagnostic test, reconnect harness connector C201 and go to next step. If any module other than PCM, ABS module and speed control servo did not pass data link diagnostic test, reconnect harness connector C201 and go to step  8.
  6. Turn ignition switch to LOCK position. Disconnect ABS module harness connector, located in right front of engine compartment, under upper radiator support. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except ABS module and speed control servo passed data link diagnostic test, replace ABS module and retest system for normal operation. If any module other than ABS module and speed control servo did not pass data link diagnostic test, go to next step.
  7. Turn ignition switch to LOCK position. Disconnect PCM harness connector located in engine compartment on left side of firewall. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except ABS module, PCM and speed control servo passed data link diagnostic test, replace PCM and retest system for normal operation. If any module other than ABS module, PCM and speed control servo did not pass data link diagnostic test, repair circuit No. 914 (Tan/Orange wire) and/or circuit No. 915 (Pink/Light Blue wire) between harness connector C201 and ABS module, PCM, speed control servo and evac and fill harness connector C133 (Tan/Orange wire only). Retest system for normal operation.
  8. Turn ignition switch to LOCK position. Disconnect 42-pin harness connector C202 located behind right side of instrument panel. See Figure. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except air suspension/Electronic Variable Orifice (EVO) steering module, Driver's Door Module (DDM) and Driver's Seat Module (DSM) (if equipped) passed data link diagnostic test, reconnect harness connector C202 and go to next step. If any module other than air suspension/EVO steering module, DDM and DSM (if equipped) did not pass data link diagnostic test, reconnect harness connector C202 and go to step  12.
  9. Turn ignition switch to LOCK position. Disconnect DDM 22-pin harness connector C520 located inside driver's door. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except DDM passed data link diagnostic test, replace DDM and retest system for normal operation. If any module other than DDM did not pass data link diagnostic test, go to next step (if equipped with a DSM) or go to step  11 (if not equipped with a DSM).
  10. Turn ignition switch to LOCK position. Disconnect DSM 26-pin harness connector C313 located under driver's front seat. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except DSM and DDM passed data link diagnostic test, replace DSM and retest system for normal operation. If any module other than DSM and DDM did not pass data link diagnostic test, go to next step
  11. Disconnect air suspension/EVO steering module Black harness connector C251. Air suspension/EVO steering module is located below right side of instrument panel. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except DSM, DDM and air suspension/EVO steering module passed data link diagnostic test, replace air suspension/EVO steering module and retest system for normal operation. If any module other than DSM, DDM and air suspension/EVO steering module did not pass data link diagnostic test, repair circuit No. 914 (Tan/Orange wire) and/or circuit No. 915 (Pink/Light Blue wire) between harness connector C202 and DSM (if equipped), DDM and air suspension/EVO steering module and retest system for normal operation.
  12. Turn ignition switch to LOCK position. Disconnect LCM 16-pin harness connector C221 located behind left side of instrument panel, right of steering column. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except LCM passed data link diagnostic test, replace LCM and retest system for normal operation. If any module other than LCM did not pass data link diagnostic test, go to next step (if equipped with front radio control unit) or go to step  14 (if not equipped with front radio control unit).
  13. 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. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except LCM and front radio control unit passed data link diagnostic test, replace front radio control unit and retest system for normal operation. If any module other than LCM and front radio control unit did not pass data link diagnostic test, go to next step.
  14. Turn ignition switch to LOCK position. Disconnect instrument cluster 12-pin harness connector C254. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except instrument cluster, LCM and front radio control unit (if equipped) passed data link diagnostic test, replace instrument cluster and retest system for normal operation. If any module other than instrument cluster, LCM and front radio control unit (if equipped) did not pass data link diagnostic test, go to next step.
  15. Turn ignition switch to LOCK position. Disconnect Electronic Automatic Temperature Control (EATC) module White harness connector C281 located behind center of instrument panel. Turn ignition switch to RUN position. Perform data link diagnostic test. See DATA LINK DIAGNOSTIC TEST  under SELF-DIAGNOSTIC SYSTEM. If all modules equipped on vehicle except EATC module, instrument cluster, LCM and front radio control unit (if equipped) passed data link diagnostic test, replace EATC module and retest system for normal operation. If any module other than EATC module, instrument cluster, LCM and front radio control unit (if equipped) did not pass data link diagnostic test, repair circuit No. 914 (Tan/Orange wire) and/or circuit No. 915 (Pink/Light Blue wire) between harness connector C202 and LCM, front radio control unit (if equipped), instrument cluster and EATC module. Retest system for normal operation.
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