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HOMESERVICE MANUALSNISSAN-DATSUN2012SENTRA SE-RREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 9 (ENGINE CONTROL SYSTEM - INTRODUCTION (MR20DE) (CALIFORNIA))SERVICE INFORMATIONPRECAUTIONSPRECAUTION
2012 Nissan-Datsun Sentra SE-R

Service Information: Precautions: Precaution

2012 Nissan-Datsun Sentra SE-RSECTION Precaution
WARNING: This page is about a different variant/trim than selected.
  • Always use a 12 V battery as power source  .
  • Never attempt to disconnect battery cables while engine is running  .
  • Before connecting or disconnecting the ECM harness connector, turn ignition switch OFF and disconnect negative battery cable. Failure to do so may damage the ECM because battery voltage is applied to ECM even if ignition switch is turned OFF  .
  • Before removing parts, turn ignition switch OFF and then disconnect negative battery cable  .
    Fig 1: Disconnecting Negative Battery Terminal
    G04874610Courtesy of NISSAN NORTH AMERICA, INC.
  • Never disassemble ECM  .
  • If battery cable is disconnected, the memory will return to the initial ECM values  .

    The ECM will now start to self-control at its initial values. Engine operation can vary slightly in this case. However, this is not an indication of a malfunction. Never replace parts because of a slight variation  .

  • If the battery is disconnected, the following emission-related diagnostic information will be lost within 24 hours  .
  • Diagnostic trouble codes 
  • 1st trip diagnostic trouble codes 
  • Freeze frame data 
  • 1st trip freeze frame data 
  • System readiness test (SRT) codes 
  • Test values 
    Fig 2: Identifying ECM
    G04886575Courtesy of NISSAN NORTH AMERICA, INC.
  • When connecting ECM harness connector, fasten (B) it securely with a lever (1) as far as it will go as shown in the figure  .
    • ECM (2) 
    • Loosen (A) 
    Fig 3: Checking Loosen And Fasten ECM Harness Connectors
    G04887003Courtesy of NISSAN NORTH AMERICA, INC.
    • When connecting or disconnecting pin connectors into or from ECM, take care not to damage pin terminals (bend or break)  .

      Make sure that there are not any bends or breaks on ECM pin terminal, when connecting pin connectors  .

    • Securely connect ECM harness connectors  .

      A poor connection can cause an extremely high (surge) voltage to develop in coil and condenser, thus resulting in damage to ICs  .

    • Keep engine control system harness at least 10 cm (4 in) away from adjacent harness, to prevent engine control system malfunctions due to receiving external noise, degraded operation of ICs, etc  .
    • Keep engine control system parts and harness dry  .
    • Before replacing ECM, perform "ECM Terminals and Reference Value" inspection and make sure ECM functions properly. Refer to "ECM TERMINAL AND REFERENCE VALUE ".
      Fig 4: Identifying Bend And Break Connector Pin
      G04874759Courtesy of NISSAN NORTH AMERICA, INC.
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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.