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Test O: Brake Indicator Inoperative/Always On

NOTE: Before testing, ensure brake fluid level is correct.
  1. Turn ignition switch to LOCK position. Connect New Generation Star (NGS) tester to Data Link Connector (DLC). DLC is located below driver's side of instrument panel, right of steering column. Turn ignition switch to RUN position. Monitor Generic Electronic Module (GEM) PIDs IGN_KEY, IGN_S, IGN_R and IGN_A while cycling ignition switch through all positions. If PIDs agree with ignition switch positions, go to next step. If PIDs do not agree with ignition switch positions, test ignition switch. See IGNITION SWITCH under COMPONENT TESTS in STEERING COLUMN SWITCHES - MUSTANG article.
  2. Using NGS tester, monitor GEM PID PRK_BRK while applying and releasing parking brake. NGS tester should display ON with parking brake applied, and OFF with parking brake released. If PID agrees with parking brake position, go to next step. If PID does not agree with parking brake position, go to step  5 .
  3. Ensure parking brake is released. Ensure ignition switch is in RUN position. If BRAKE indicator is not illuminated, go to next step. If BRAKE indicator is illuminated, go to step  10 .
  4. Using NGS tester, trigger GEM active command BKFLD LOW on. If BRAKE indicator illuminates, go to step  13 . If BRAKE indicator does not illuminate, go to step  8 .
  5. Using NGS tester, monitor GEM PID PRK_BRK while applying and releasing parking brake. NGS tester should display ON with parking brake applied, and OFF with parking brake released. If PID agrees with parking brake position, go to step  7 . If PID does not agree with parking brake position, go to next step.
    6. NOTE: The wire connected between parking brake switch harness connector C318 and 12-pin Generic Electronic Module (GEM) harness connector C293 terminal No. 4 is Violet/Yellow at GEM and switches to Light Blue/Black at splice S246. Splice S246 is located near lower left "A" pillar.
  6. Turn ignition switch to LOCK position. Disconnect 12-pin Generic Electronic Module (GEM) harness connector C293. GEM is located behind left side of instrument panel, next to central junction box. Disconnect parking brake switch harness connector C318. Parking brake switch is located on parking brake lever assembly. Measure resistance between Light Blue/Black wire terminal at parking brake switch harness connector C318 and GEM harness connector C293 terminal No. 4 (Violet/Yellow wire). See Figure . If resistance is 5 ohms or less, replace parking brake switch. If resistance is more than 5 ohms, repair open in wire between parking brake switch and GEM. See WIRING DIAGRAMS in MODULE COMMUNICATIONS NETWORK - MUSTANG article.
    7. NOTE: The wire connected between parking brake switch harness connector C318 and Generic Electronic Module (GEM) harness connector C293 terminal No. 4 is Violet/Yellow at GEM and switches to Light Blue/Black at splice S246. Splice S246 is located near lower left "A" pillar.
  7. Turn ignition switch to LOCK position. Disconnect 12-pin Generic Electronic Module (GEM) harness connector C293. GEM is located behind left side of instrument panel, next to central junction box. Disconnect parking brake switch harness connector C318. Parking brake switch is located on parking brake lever assembly. Measure resistance between ground and GEM harness connector C293 terminal No. 4 (Violet/Yellow wire). See Figure . If resistance is more than 10 k/ohms, replace parking brake switch. If resistance is 10 k/ohms or less, repair short to ground in wire between parking brake switch and GEM. See WIRING DIAGRAMS  .
  8. Turn ignition switch to LOCK position. Disconnect 26-pin Generic Electronic Module (GEM) harness connector C352. GEM is located behind left side of instrument panel, next to central junction box. Disconnect 20-pin instrument cluster harness connector C251. It may be necessary to remove instrument cluster for access to connector. See REMOVAL & INSTALLATION  . Turn ignition switch to RUN position. Measure voltage at GEM harness connector C352 terminal No. 13 (Violet/Yellow wire). See Figure . If voltage does not exist, go to next step. If voltage exists, repair short to voltage in Violet/Yellow wire between GEM, instrument cluster and brake fluid level sensor. See WIRING DIAGRAMS  .
  9. Turn ignition switch to LOCK position. Measure resistance in Violet/Yellow wire between GEM harness connector C352 terminal No. 13 and instrument cluster harness connector C251 terminal No. 14. See Figure and Figure . If resistance is 5 ohms or less, go to step  14 . If resistance is more than 5 ohms, repair open in Violet/Yellow wire between GEM and instrument cluster. See WIRING DIAGRAMS  .
  10. Turn ignition switch to LOCK position. Disconnect brake fluid level sensor harness connector C164. Brake fluid level sensor is located on brake fluid reservoir. Turn ignition switch to RUN position. Ensure parking brake is released. If BRAKE indicator is illuminated, go to next step. If BRAKE indicator is not illuminated, replace brake fluid level sensor.
  11. Turn ignition switch to LOCK position. Disconnect 26-pin Generic Electronic Module (GEM) harness connector C352. GEM is located behind left side of instrument panel, next to central junction box. Turn ignition switch to RUN position. If BRAKE indicator is illuminated, go to next step. If BRAKE indicator is not illuminated, go to step  13 .
  12. Turn ignition switch to LOCK position. Disconnect 20-pin instrument cluster harness connector C251. It may be necessary to remove instrument cluster for access to connector. See REMOVAL & INSTALLATION  . Measure resistance between ground and GEM harness connector C352 terminal No. 13 (Violet/Yellow wire). See Figure . If resistance is more than 10 k/ohms, go to step  14 . If resistance is 10 k/ohms or less, repair short to ground in Violet/Yellow wire between GEM and instrument cluster. See WIRING DIAGRAMS  .
  13. Disconnect all GEM harness connectors. Inspect all GEM harness connectors for loose, damaged or corroded terminals. If terminals are damaged, repair as necessary. If terminals are not damaged, reconnect all GEM harness connectors. Ensure GEM harness connectors are seated properly. If problem still exists, replace GEM. See REMOVAL & INSTALLATION  .
  14. Disconnect all instrument cluster harness connectors. Inspect all instrument cluster harness connectors for loose, damaged or corroded terminals. If terminals are damaged, repair as necessary. If terminals are not damaged, reconnect all instrument cluster harness connectors. Ensure instrument cluster harness connectors are seated properly. If problem still exists, replace instrument cluster module.
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