AT/Automatic Transmission — Trouble No. 3 No up-shift to overdrive (After warm up), page 26

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)