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)