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Sentra 1.8L

  1. Turn ignition on. Measure voltage by backprobing between ground and PCM harness connector terminal No. 50 (Red/White wire). See Figure. With rear window defogger on, battery voltage should exist. With rear window defogger off, zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step  4.
  2. Measure voltage by backprobing between ground and PCM harness connector terminal No. 50 (Red/White wire). With headlights on, battery voltage should exist. With headlights off, zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step  6.
  3. Measure voltage by backprobing between ground and PCM harness connector terminal No. 51 (Light Green/Black wire). With blower fan on, battery voltage should exist. With blower fan off, zero volts should exist. If voltage is as specified, go to step  10. If voltage is not as specified, go to step  8.
  4. Start engine. Turn rear window defogger on. If rear window warms up, go to next step. If rear window does not warm up, repair rear window defogger. See appropriate REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT.
    CAUTION: Blue/Red wire from rear window defogger relay changes to Red/White wire at diode No. 3, terminal No. 2 located near fuel pump relay at left kick panel. See Figure. Wire is Red/White at PCM connector terminal No. 50.
  5. Stop engine. Disconnect rear window defogger relay, located next to fuel pump relay behind left kick panel. Disconnect PCM harness connector. Check continuity of Blue/Red wire between PCM harness connector terminal No. 50 and rear window defogger relay harness connector terminals No. 5 and 7. See Figure and Figure . If continuity exists, go to step  10. If continuity does not exist, repair open in Blue/Red wire.
  6. Start engine. Turn headlights on. If headlights illuminate, go to next step. If headlights do not illuminate, repair lighting system. See HEADLIGHT SYSTEMS article in ACCESSORIES & EQUIPMENT.
    CAUTION: Red/Yellow wire from headlight switch changes to Red/White wire at diode No. 3, terminal No. 2 located near fuel pump relay at left kick panel. Wire is Red/White at PCM connector terminal No. 50.
  7. Stop engine. Turn ignition off. Disconnect headlight switch harness and PCM harness connectors. Check continuity of Red/Yellow wire between headlight switch harness connector terminal No. 10 and PCM harness connector terminal No. 50. If continuity does not exist, repair open in Red/Yellow wire. If continuity exists, go to step  10.
  8. Start engine. Turn heater fan on. If fan motor operates, go to next step. If fan motor does not operate, repair blower motor. See appropriate MANUAL OR AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  9. Stop engine. Disconnect heater fan control switch harness and PCM harness connectors. Check continuity of Light Green/Black wire between heater fan control switch harness connector terminal No. 6 and PCM harness connector terminal No. 51. Also check continuity of Black wire between ground and heater fan control switch harness connector terminal No. 5. If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire. See appropriate wiring diagram in WIRING DIAGRAMS article.
  10. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.
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