Power & Ground Circuits (Sentra 2.5L)

Start engine. If engine starts, go to step 9. If engine does not start, go to next step.
Turn ignition off and on. Backprobing at ECM, measure voltage between ground and ECM terminal No. 42 (Black/Red wire). See Figure and Figure . If battery voltage does not exist, go to next step. If battery voltage exists, go to step 4.
Check the following:
- Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors M19 and E108. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
- Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors E10 and F48.
- Check for poor, loose, corroded or damaged terminal connections in fuse block harness connectors E112 and M1.
- Check fuse block fuse No. 17 (10-amp).
- Check for open or short in circuits between ECM and fuse.
If problem is found, repair as necessary. After repair, retest system.
Turn ignition off. Disconnect ECM 116-pin harness connector. ECM is located under instrument panel. See Figure. Check continuity between ground and ECM harness connector terminal No. 59 (Black/Red wire). Check continuity between ground and ECM harness connector terminals No. 60, 106 and 108 (Black wires). See Figure. Continuity should exist at each measurement. Also, check circuits for short to voltage. If problem is found, go to next step. If no problem is found, go to step 6.
Check the following:
- Check for poor, loose, corroded or damaged terminal connections in joint connector-3. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
- Check for open or short in circuits between ground and ECM.
If problem is found, repair as necessary. After repair, retest system.
Disconnect ECM relay. See Fig 1. Measure voltage between ground and ECM relay harness connector terminals No. 1 (White/Blue wire) and No. 6 (Red/Black wire). See Figure. If battery voltage does not exist, go to next step. If battery voltage exists, leave harness connectors disconnected and go to step 8.
Check the following:
- Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors E9 and F47. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
- Check fuse block fuses No. 34 and 36 (15-amp).
- Check for poor, loose, corroded or damaged terminal connections in underhood fuse and fusible link box harness connectors E22 and E24.
- Check for open or short in circuits between battery and ECM relay.
If problem is found, repair as necessary. After repair, retest system.
Check continuity of White/Green wire between ECM harness connector terminal No. 20 and ECM relay harness connector terminal No. 2. See Figure and Figure . Also, check circuit for short to ground and short to voltage. If no problem is found, check ignition signal. Perform appropriate procedure under IGNITION SIGNAL CIRCUITS . If problem is found, repair as necessary. After repair, retest system.
Turn ignition on, and then off. Backprobing at ECM, measure voltage between ground and ECM terminals No. 12 (Red wire), and then No. 109 and 111 (Red/Green wires). Battery voltage should exist at each terminal for a few seconds after turning ignition off, then drop to about zero volts. If voltage is as specified, go to step 13. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step 12.
Disconnect ECM relay. See Fig 1. Measure voltage between ground and ECM relay harness connector terminals No. 3 (White/Blue wire). See Figure. If battery voltage does not exist, go to next step. If battery voltage exists, leave ECM relay disconnected and go to step 12.
Check the following:
- Check for poor, loose, corroded or damaged terminal connections at in-line harness connectors E9 and F47. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
- Check for open or short in circuits between ECM relay and fuses.
If problem is found, repair as necessary. After repair, retest system.

Check continuity of specified circuits between ECM and ECM relay. See CHECKING ECM RELAY CIRCUIT VOLTAGE (SENTRA 2.5L) table. See Figure and Figure . Also, check circuit for short to ground and short to voltage. If no problem is found, go to next step. If problem is found, repair as necessary. After repair, retest system.

CHECKING ECM RELAY CIRCUIT VOLTAGE (SENTRA 2.5L)

ECM Terminal No.	ECM Relay Terminal No.	Wire Color
12	7	Red
109 & 111	5	Red/Green

Working with ECM relay, apply battery voltage and ground to terminals No. 1 and 2. See Figure. When battery voltage is applied, continuity should exist between terminals No. 3, 5, 6 and 7. When battery voltage is removed, continuity should not exist. If relay tests okay, go to next step. Replace relay, if test values are not as specified.
Turn ignition off. Disconnect ECM 116-pin harness connector. ECM is located under instrument panel. See Figure. Check continuity between ground and ECM harness connector terminal No. 59 (Black/Red wire). Check continuity between ground and ECM harness connector terminals No. 60, 106 and 108 (Black wires). See Figure. Continuity should exist at each measurement. Also, check circuits for short to voltage. If problem is found, go to next step. If no problem is found, go to step 16.
Check the following:
- Check for poor, loose, corroded or damaged terminal connections in joint connector-3. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
- Check for open or short in circuits between ground and ECM.
If problem is found, repair as necessary. After repair, retest system.
No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.

Fig 1: Locating Engine Control Module Relay (Sentra)

Courtesy of NISSAN MOTOR CO., U.S.A.