Nissan 55-50/51SN Electronic Functions

Valve Body Xpress

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Normal Shifting Programs

  • Economy Mode - Under normal acceleration, the TCM provides earliest possible upshifts and lockup for best economy. Oil pressure is adjusted to provide smooth shifts and engagements.
  • Sport Mode - If the accelerator is pressed quickly and speed exceeds 31MPH, shift points are raised to provide the best performance. Downshift occurs at lower engine RPM. If the accelerator is moved less quickly, the TCM automatically resumes economy mode.
  • Extreme Mode - Another way of saying "kickdown." The TCM selects the lowest gear for vehicle speed when the throttle is depressed to the floor.
  • Winter Mode - Use the "W" button on the top panel of the gear selector assembly. A warning lamp on the instrument cluster illuminates and the transmission starts in 3rd gear to provide maximum traction. Depending on the gear selected, the following can occur:
    • D - Starts in 3rd and automatically shifts between 3rd, 4th, and 5th.
    • 4 - Starts in 3rd and automatically shifts to 4th earlier than economy in D range, with 5th gear locked out.
    • 3 - Starts in 3rd with no up/downshifts.
    • L - Starts in 2nd with no up/downshifts.
    • At wide open throttle in winter mode, all gears are used for max performance.
  • Catalytic Converter Start - Helps reach operating temperature, prevents converter lock-up and delays 1-2 and 2-3 upshift when cold. This is normal function.
  • Temperature Controlled Lockup - If temperature rises excessively due to heavy load with high ambient temp conditions, the torque converter clutch applies to reduce heat. If temperature drops below 20°C (68°F), lockup is inhibited.
  • Slipping Lockup - Gives smoother lockup and reduces vibration/noise. Computer maintains 50-200 RPM torque converter clutch slip. The following conditions must be met:
    • Gear shift must be in D, 4 or 3.
    • Transmission must be in 3rd, 4th or 5th.
    • Transmission input speed must be 1100 RPM or higher.
    • Throttle opening must be 35% or less.
    • Engine coolant must reach certain temperature. Trans oil temperature must be 40°C (104°F), but not exceed 120°C (248°F). NOTE: Friction properties of this transmission fluid are different due to large amount of converter clutch slip. Failure to use correct fluid will cause transmission damage and codes.
  • Driving Uphill - To reduce shift business, the TCM may change the shift pattern slightly when driving uphill.
  • Neutral Control - Not available on all models. The TCM disengages forward clutch (CI) at stop, with the brake applied to reduce load. Reduces vibration/improves fuel economy. When the brake is released, the forward clutch engages. The following conditions must be met:
    • Manual shift must be in D, 4 or 3.
    • Does NOT work in Winter Mode or Geartronic.
    • Transmission oil temperature must be above 10°C (50°F).
    • Throttle position must be less than 3%.
    • Brake must be pressed.
    • Speed must be 0 MPH.
    • Engine speed must be less than I500 RPM.
    • There's a 2 second delay once vehicle has stopped in D, and a 5 second delay from N-D.

Shifting Using Geartronic

When the shifter is moved to Geartronic, the transmission remains in hydraulic "D" position. When the shifter is moved to + or - positions, the gear selector module sends a signal to the TCM to shift the transmission up or down. The driver information module changes the symbol on the instrument panel from D to the gear that's selected, and a signal is sent to the gear selector module to light M and turn off other LEDs on the shifter console. The TCM determines if the shift can be carried out and activates appropriate solenoids. The TCM overrides driver's command under certain circumstances.


Nissan Shift Adapts

To clear the shift adapts, a Nissan factory specific scanner (Consult Scan Tool) must be used. The EEPROM in the TCM is erased and reset to the default settings during a process that Nissan refers to as "TCM Initialization." Following is a list of things that can be adapted and must be learned by the TCM for proper shift and engagement feel:

  • Up/Down Shift Control - the TCM learns the correct pressure for each shift.
  • N-D Engagement - the TCM learns the correct forward clutch pressure for a good forward engagement.
  • N-R Engagement - the TCM learns the correct direct clutch pressure for a good reverse engagement.
  • Torque Reduction Control - the TCM learns the correct amount of engine torque reduction to request during up and down shifting as well as N-D and N-R engagements.

At this time, no aftermarket scan tool is capable of performing the TCM Initialization, nor is there a manual reset procedure.

PLEASE NOTE: After resetting the shift adapts, the vehicle must be driven 70 to 100 shift cycles through all of the gears at about 20% throttle angle while at operating temperature. This procedure will relearn the shift adapts. Follow the Saturn relearn procedure to relearn the engagements.

Nissan Service Bulletin #NTBOS-026

TCM reprogramming needed when replacing a 5-Speed A/T.
This bulletin applies to 2004-05 Maxima and 2005 Altima with 5- speed automatic transaxle.

Related Part(s)
Related Unit(s)
Subject(s) Included
  • General Diagnostics and Theory

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