NATS (Nissan Anti-Theft System) / Gasoline engine — Trouble Diagnoses (Cont'd) — Diagnostic Procedure 2 (CHAIN OF ECM-IMMU) (Supplement-VII)
EL-7066flowchartProcedure 2: CHAIN OF ECM-IMMU harness check. Tests battery (C1), ignition (C2), ground (C3), and ECM↔IMMU communication (C4) in sequence.
Trouble Diagnoses (Cont'd)
DIAGNOSTIC PROCEDURE 2
Self-diagnostic results: 'CHAIN OF ECM-IMMU' displayed on CONSULT-II screen
Procedure 2 — CHAIN OF ECM-IMMU communication-line fault
1
[A] Confirm SELF-DIAGNOSTIC RESULTS 'CHAIN OF ECM-IMMU' displayed on CONSULT-II screen.
2
[B] CHECK POWER SUPPLY CIRCUIT FOR IMMU. Check voltage between terminal 8 of IMMU and ground. Voltage: Battery voltage.
NG
Check 10A fuse [No. 20] in fuse block (J/B); Harness for open or short between fuse and IMMU connector. Ref. part No. C1.
OK
3
[C] CHECK IGN SW. ON SIGNAL. Check voltage between terminal 7 of IMMU and ground while ignition switch is in 'ON' position. Voltage: Battery voltage.
NG
Check 10A fuse [No. 25] in fuse block (J/B); Harness for open or short between fuse and IMMU connector. Ref. part No. C2.
OK
4
[D] CHECK GROUND CIRCUIT FOR IMMU. Check harness continuity between IMMU terminal 4 and ground. Continuity should exist.
NG
Repair harness. Ref. part No. C3.
OK
5
[E] CHECK COMMUNICATION ON OPEN CIRCUIT. Check harness continuity between ECM terminal 88 and IMMU terminal 1. Continuity should exist.
NG
Repair harness. Ref. part No. C4.
OK
6
→ Continue with [A] on next page (NEL flow).
NOTE
*: In rare case, 'CHAIN OF ECM-IMMU' might be stored during key registration procedure, even if the system is not malfunctioning.
Procedure 2 isolates harness faults on the IMMU side:
• Step B → fuse 10A [No. 20] (battery line, C1)
• Step C → fuse 10A [No. 25] (ignition line, C2)
• Step D → ground continuity (C3)
• Step E → communication line ECM pin 88 ↔ IMMU pin 1 (C4)
If all four steps pass, continue with step [A] on the next page (further IMMU/ECM testing).