2004 Nissan-Datsun Sentra SE-RFACTORY OEM SERVICE PROCEDURE

Section 2313 (Engine Control System - Introduction): Precautions: Precaution

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.
  • Always use a 12 volt battery as power source  .
  • Do not 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 MOTOR CO., U.S.A.
  • Do not disassemble ECM  .
  • If a battery cable is disconnected, the memory will return to the ECM value  .

    The ECM will now start to self-control at its initial value. Engine operation can vary slightly when the terminal is disconnected. However, this is not an indication of a malfunction. Do not 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 
  • When connecting ECM harness connector, fasten it securely with levers as far as they will go as shown in the figure  .
    Fig 2: Identifying ECM
    G04899963Courtesy of NISSAN MOTOR CO., U.S.A.
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.

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