Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

2012 Nissan-Datsun Sentra SE-RFACTORY OEM SERVICE PROCEDURE

Key Switch (BCM Input) Check

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 M49 terminal 2 and ground.
  2 - Ground: Battery voltage .
  
  Fig 1: Checking Key Switch Power Supply Circuit
  Courtesy of NISSAN NORTH AMERICA, INC.
  
  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 1 and 2.

Component	Terminals		Condition	Continuity
Ignition switch	1	2	Insert mechanical key into ignition switch.	Yes
Ignition switch	1	2	Remove mechanical key from ignition switch.	No

Fig 2: Checking Key Switch

G04916811

Courtesy of NISSAN NORTH AMERICA, INC.

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 (A) terminal 37 and key switch and ignition knob switch harness connector M49 (B) terminal 1.
  37 - 1: Continuity should exist .
3. Check continuity between BCM harness connector M18 (A) terminal 37 and ground.
  37 - Ground: Continuity should not exist .
  
  Fig 3: Checking Key Switch Signal Circuit
  Courtesy of NISSAN NORTH AMERICA, INC.
  
  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.

Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.