AT/Automatic Transmission — Trouble No. 4 No up-shift to overdrive (After warm-up), page 16

AT-16                    AUTOMATIC TRANSMISSION — Electric Control

Trouble No. 4        No up-shift to overdrive (After warm-up)

Road test while shifting manually with ECT ECU
connector pulled out. Is there overdrive up-shift in D
range when shifting from L to 2 to D?
                                                          No ——→ Faulty transmission
           ↓
          Yes
           ↓
Connect ECT ECU connector, and                            0 → 7V    • Faulty transmission
while driving does DG terminal voltage                              • Faulty solenoid
rise from 0V to 7V in sequence?
           ↓
    0 → 5V              0V
           ↓               ↓
                           ↓————————————→ 0 → 3V    There is 12V between ECT ECU terminals
                                                    2 and GND when D range.
                                              ↓                                    ↓
                                             Yes                                  No
                                              ↓                                    ↓
                           There is 12V between ECT ECU
                           terminals L and GND when D range.
                                              ↓
                                    No        ↓        Yes
                                     ↓        ↓         ↓
                                     ↓        ↓    • Faulty neutral start switch circuit
                                     ↓        ↓    • Faulty neutral start switch
                                     ↓        ↓         ↓
                                     ↓        ↓———→ Try another ECT ECU ←————————┘
                                     ↓
                                     ↓
Is voltage between terminals OD₃ and GND as                  • Faulty OD switch
follows?                                        No ————→       harness
  OD switch turn ON:   12V (Aisin) or 5V (Denso)              • Faulty OD switch
  OD switch turn OFF:  0V                                     • OD off light open
           ↓
          Yes
           ↓
    (Check OD cutout signal)
           ↓
Is voltage between terminals OD and GND as follows?
  Approx.    5V (Denso) or 12V (Aisin)              Yes ——→ Try another ECT ECU
  (coolant temp. above 70°C or 158°F)
           ↓
          No
           ↓
    (Check OD cutout signal)
           ↓
Is voltage between ECU terminals
OD₁ and GND normal with the cruise                   Yes ——→ Faulty cruise control computer
control computer connector pulled out?
                                                     No ——→ Faulty engine ECU
                                                            (Short circuit in ECT wire harness
                                                             or EFI water temp. sensor bad)