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Power & Ground Circuits (Sentra)

  1. Start engine. If engine starts, go to next step. If engine does not start, turn ignition off and on. Measure voltage between ground and PCM harness connector terminal No. 43 (Black/Red wire) by backprobing. See Figure and Fig 1 . If battery voltage exists, go to step  8. If battery voltage does not exist, repair open or short circuit between PCM and fuse block. See appropriate wiring diagram in WIRING DIAGRAMS article.
    Fig 1: Locating PCM Harness Connector (Sentra)
    G00015113Courtesy of NISSAN MOTOR CO., U.S.A.
  2. Stop engine. Measure voltage between ground and PCM harness connector terminal No. 67 (White/Blue wire) by backprobing. See Figure. If battery voltage exists, go to next step. If battery voltage does not exist, repair short or open circuit between PCM and fuse block. See appropriate wiring diagram in WIRING DIAGRAMS article.
  3. While turning ignition on and off, measure voltage between ground and PCM harness connector terminals No. 110 and 112 (White wires) by backprobing. Battery voltage should exist for a few seconds after turning ignition off. If voltage is as specified, go to step  8. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step  7.
  4. Turn ignition off. Remove ECCS relay. See Fig 2. Disconnect PCM harness connector. Check continuity of White wire between PCM terminals No. 110 and 112 and ECCS relay terminal No. 5. See Figure and Figure . If continuity exists, go to next step. If continuity does not exist, repair short or open circuit between PCM and ECCS relay.
    Fig 2: Locating ECCS Relay (Sentra)
    G00015114Courtesy of NISSAN MOTOR CO., U.S.A.
  5. Measure voltage between ground and ECCS relay terminals No. 1 and 3. See Figure and Figure . If battery voltage exists, go to next step. If battery voltage does not exist, repair short or open circuit between PCM and ECCS relay.
  6. Turn ignition off. Measure continuity between ECCS relay harness terminal No. 2 and PCM harness connector terminal No. 31 (White/Green wire). See Figure and Figure . If continuity exists, go to next step. If continuity does not exist, repair open or short in White/Green wire between PCM and ECCS relay.
  7. Check ECCS relay. See RELAYS  under RELAYS & SOLENOIDS. Replace, if necessary and retest system. If relay is okay, go to next step.
  8. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminal Nos. 48 and 57 (Black wires) and terminal Nos. 106 and 108 (Black/Yellow wires). If continuity exists, go to next step. If continuity does not exist, repair open or short in ground circuit(s).
  9. 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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