1994 Toyota 4Runner automatic transmission wont shift into

FORERUNNIN

MEMBER
1994 TOYOTA 4RUNNER
6 CYL
4WD
AUTOMATIC
156,000 MILES

I just purchased a 1994 Toyota 4runnner.A few days ago I noticed that the trans won't shift into overdrive early into the drive. Not until it warms up. Its as if it in 2l on the shifter. If I hit the o/d button nothing happen. Once the trans warms it will shift. And o/d button works. It scares me cause I find myself going down the road at 55 mph and the tach at 4500 rpms. What could the problem be? I checked the fluid and it hard to get a good reading. I was also thinking of getting a trans flush done. Your thoughts on this would be greatly appreciated. I was also thinking of putting Mobil 1 in. Is that a bad move with the high mileage? Thanks for your time.

Mike in jersey

1 Reply

KHLOW2008

MECHANIC
41,814 POSTS

Hi forerunnin,

Thank you for the donation.

Here are the description and diagnostics for OD not upshifting.

NO UPSHIFT TO OVERDRIVE

1. Warm engine to normal operating temperature. With ignition off, disconnect electrical connector for solenoid from rear of transmission.

2. Road test vehicle and note if transmission upshifts to Overdrive once transmission shifts from "L" to "2" and then into "D" range. Reconnect electrical connector. Clear trouble codes from ECU memory, as disconnecting ECT ECU electrical connector may set trouble codes. If no overdrive upshift exists, transmission is defective. If overdrive upshift exists, proceed to step next step.

3. Connect voltmeter between terminals TT and E1 of data link connector. See Fig. 18

4. Road test vehicle and ensure voltage at terminal TT increases from zero to 7 volts. If no voltage exists, check for 12 volts between terminals "L" and E1 on ECT ECU with connector installed on ECT ECU and shift lever in "D" position with ignition on. See Fig. 25. If 12 volts exist, check for defective park/neutral position switch or wiring circuit. If 12 volts do not exist, replace ECT ECU.

5. If voltage increases from zero to 3 volts, check for 12 volts between terminals "2" and E1 on ECT ECU with connector installed on ECT ECU and shift lever in "D" position with ignition on. If 12 volts exist, check for defective neutral start switch or wiring circuit. If 12
volts do not exist, replace ECT ECU.

6. If voltage increases from zero to 7 volts, transmission or solenoid is faulty. If voltage increases from zero to 5 volts, connect voltmeter between terminals OD2 and E1 on ECT ECU with connector installed on ECT ECU.

7. Turn ignition on. Check voltage with OD switch in released (OFF position) and depressed (ON position). No voltage should exist with switch released and 10-14 volts with switch depressed.

8. If voltage is correct, proceed to next step. If voltage is not correct, check for defective OD
switch or wiring circuit.

9. Check voltage between terminals OD1 and E1 on ECT ECU with connector installed on ECT ECU and ignition on. Voltage should be about 5 volts. If voltage is correct, replace ECT ECU. If voltage is not correct, proceed to next step.

10. Disconnect electrical connector from cruise control Electronic Control Unit (ECU). See Fig. 9. Check voltage between terminals OD2 and E1 on ECT ECU with connector installed on ECT ECU and ignition on. If voltage is now about 5 volts, replace cruise control ECU. If voltage is not about 5 volts, check for defective cruise control ECU wiring. If wiring is okay, replace ECT ECU.