Key Switch (BCM Input) Check

WARNING: This page is about a different car, the 2008 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.

CHECK KEY SWITCH POWER SUPPLY CIRCUIT
1. Remove mechanical key from ignition switch.
2. Disconnect key switch and ignition knob switch connector.
3. Check voltage between key switch and ignition knob switch harness connector M73 terminal 3 and ground.
  3 - Ground: Battery voltage.
Fig 1: Checking Voltage Between Key Switch And Ignition Knob Switch Connector M118 Terminal 3 And Ground
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG

OK: GO TO 2.

NG: Check harness between key switch and ignition knob switch and fuse.

CHECK KEY SWITCH

Check continuity between key switch and ignition knob switch terminals 3 and 4.

KEY SWITCH AND IGNITION KNOB SWITCH TERMINALS 3 AND 4

Component	Terminals		Condition	Continuity
Ignition switch	3	4	Insert mechanical key into ignition switch.	Yes
Ignition switch	3	4	Remove mechanical key from ignition switch.	No

Fig 2: Checking Continuity Between Key Switch And Ignition Knob Switch Connector M118 Terminals 3 And 4

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

OK or NG

OK: GO TO 3.

NG: Replace key cylinder assembly (built-in key switch).

CHECK KEY SWITCH SIGNAL CIRCUIT
1. Disconnect BCM connector.
2. Check continuity between BCM harness connector M18 terminal 37 and key switch and ignition knob switch harness connector M73 terminal 4.
  37 - 4: Continuity should exist.
3. Check continuity between BCM harness connector M18 terminal 37 and ground.
  37 - Ground: Continuity should not exist.
Fig 3: Checking Continuity Between BCM Harness, Key Switch And Ignition Knob Switch Harness Connector Terminal
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG

OK: Key switch (BCM input) circuit is OK.

NG: Repair or replace harness between key switch and ignition knob switch and BCM.