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Home >> GMC >> 1996 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panel - Gasoline >> Testing >> Daytime Running Lights (DRL) >> Daytime Running Lamps (DRL) Inoperative

Daytime Running Lamps (DRL) Inoperative

  1. Ensure park/brake is off. Turn ignition switch to RUN. If "Brake" indicator is not lit, go to next step. If "Brake" indicator is lit, diagnose brake warning system. See BRAKE WARNING SYSTEM  .
  2. Turn ignition switch to "Lock." Disconnect daytime running lamps (DRL) module connector. Turn ignition switch to RUN. Connect test lamp from DRL module connector terminal "C" to ground. If test lamp lights, go to next step. If test lamp does not light, service/repair open in Pink wire between instrument panel fuse block and DRL module.
  3. Connect a test lamp from DRL module connector terminal "C" to "H". If test lamp lights, go to next step. If test lamp does not light, service/repair open in Black wire between DRL module and ground.
  4. Remove DRL relay from convenience center. Connect a test lamp from DRL relay terminal "G6" to ground. If test lamp lights, go to next step. If test lamp does not light, service/repair open in Orange wire between instrument panel fuse block and Diode 203. If okay, service/repair open in Yellow wire between Diode 203 and convenience center. If okay, locate and replace Diode 203.
  5. Connect a test lamp from DRL relay terminal "G4" to ground. If test lamp lights, go to next step. If test lamp does not light, service/repair open in Pink wire between splice and convenience center.
  6. Turn ignition switch to "Lock." Reconnect DRL module connector. Turn ignition switch to RUN. If DRL indicator is lit, go to next step. If DRL indicator is not lit, check for poor connection or damaged terminals at DRL module connector. If okay, replace DRL module.
  7. Connect digital multimeter from DRL relay terminal "H6" to battery positive terminal and measure voltage. If more than 10 volts, go to next step. If less than 10 volts exist, service/repair open in Light Green/Black wire between DRL module and convenience center.
  8. Connect fused jumper from DRL relay terminal "G6" to "H4". If low beam headlamps do not light, go to next step. If low beam headlamps light at low intensity, replace DRL relay.
  9. Reinstall DRL relay. Turn ignition switch to RUN and disconnect headlamp connector. Connect a test lamp from terminal "A" to ground. If test lamp lights, go to next step. If test lamp does not light, service/repair open in Tan wire between DRL relay and left Hi/Lo beam headlights.
  10. Using a self-powered test lamp, connect between terminal "B" and ground. If test lamp does not light, service/repair open in Dark Blue wire between left Hi/Lo beam headlamps to splice and/or service/repair open in Black wire between right Hi/Lo beam headlamp. If test lamp lights, replace left and right Hi/Lo beam headlamp.
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