AT-26 AUTOMATIC TRANSMISSION — Troubleshooting (Electronic Control System) Trouble No. 3 No up-shift to overdrive (After warm up) Road test while shifting with ECT ECU connector pulled out. Is there over- drive up-shift in the D range when shifting from L to 2 to D? Yes → No → Faulty transmission Connect ECT ECU connector, and while driving does check connector Tt voltage rise from 0 V to 7 V in sequence? 0 ~ 7V → • Faulty transmission • Faulty solenoid 0V 0 ~ 5V 0 ~ 3V → Are there 12V between ECT ECU terminals 2 and GND when in the D range? Yes → No Are there 12V between ECT ECU terminals L and GND when in the D range? No → Yes → • Faulty neutral start switch circuit • Faulty neutral start switch Try another ECT ECU Is voltage between terminals OD+ and GND as follows? O/D switch turn ON : 12V O/D switch turn OFF: 0V No → • Faulty O/D switch harness • Faulty O/D switch Yes (Coolant temp. above 60°C or 140°F) Is voltage between terminals OD+ and GND as follows? Approx. 12V Yes → Try another ECT ECU No Is voltage between ECT ECU terminals OD+ and GND normal with the cruise control ECU connector pulled out? Yes → Faulty cruise control ECU No Faulty Engine ECU (Short circuit in ECT wire harness or EFI water temp. indicator switch)