Not shifting into overdrive

I have a '99 Tacoma 3.4/4x4/automatic with 180k miles. I have owned this truck for 2+ years, and finally got it back on the road after a lot of frame, suspension and steering work. It's actually in awesome shape now. All the time I have owned it, it has never shifted into overdrive. I have done the following:

- Dropped the pan, replaced the filter
- Replaced the transmission temperature sensor

...to no avail. I can put it in diagnostic mode, and it goes into overdrive (manually) just fine. I figure that rules out the solenoid.

Next steps are focusing on electronics. Does this truck have a separate TCU, or are the transmission controls built into the ECU?

Thanks for any help.

 

What is the coolant temperature getting up to? It may not let it go into overdrive unless it's warmed up past a certain temperature. Check what the live data is reporting with an OBD2 scanner.

 

In order to achieve 4th gear as well as converter clutch lock up , many parameters have to be met .
Brake switch , throttle position , transmission temperature as well as engine temp and 3rd gear switch should all be looked at . How about the overdrive cancel switch on the shifter ? does it work ?
how are you manually selecting overdrive in diagnostic mode to make the transmission shift into overdrive ?
https://www.tacomaworld.com/threads...sions-write-up-your-4-speed-automatic.325531/

 

I did test and verify that the overdrive cancel switch is correctly opening and closing pins 5 and 10 at the wiring harness. The light on the dash goes on and off appropriately, and does not blink. Today I will hook up a OBD2 scanner to check temps.

Gearcruncher: here is the procedure I am following to manually select overdrive:

 

That should be the A340F transmission but its not uncommon for guys to change out the transmission to something different
I was going to ask if your speedometer was working ? The ECU needs to see vehicle speed and shifter position
Does the scanner show the vehicle speed as well as shifter detent position ? does the truck only start in park and nuetral and does the scanner see when you apply the brakes
was the bottom of the transmission pan nice and clean ? no metal or brass ?
Is your torque converter lock up clutch functioning ?
Just to confirm , is there a cable going from the throttle down to the transmission ?

 

Yes, it should be the A340F. It does have a throttle cable going from the throttle body down to the transmission. Here's some additional info from today:

- ODB2 engine coolant temp showed 188-192 when warmed up
- ODB2 vehicle speed matches the speedo (and speedo works)
- There are no DTC codes, and all "live" data seems normal: RPM, MPH, MAF, TPS, IAT temp (65)
- Scanner does not show shifter detent position
- Scanner does not show when brakes applied
- Vehicle only starts in P and N
- Can't tell if torque converter lockup clutch is working, but there is no slippage and transmission shift/pulls perfectly
- Transmission pan was clean when I pulled it. The magnets had nothing more than metal "dust" from 180k miles of driving

Is there a switch in the shifter that tells the ECU the shifter position? (Other than the Park-Neutral switch on the side of the trans)

Thanks for the input.

 

I am still a little confused about the manual shifting test .
You remove the wiring that powers the solenoid on the side of the transmission , then take the truck for a drive and manually upshift from 1st to 2nd to 3rd gear and then manually into drive range ( D ) and the transmission upshifts into overdrive ?
This seems backwards to the way I test for overdrive and lock up . Generally I had to manually fool the transmission by powering up the solenoid with 12 volts for overdrive . I performed this test on the hoist after the transmission shifted into 3rd gear . The transmission wont upshift to overdrive unless the ecm knows the transmission has already upshifted to 3rd .
Do you remember how many solenoids you have ?

There is a test for the nuetral safety switch on page 77 of this pdf manual

 

After removing the solenoid wiring harness, shifting is manual. I start off in L, which is 1st, then move the lever to 2, which actually selects 3rd gear (2nd gear is skipped). Then I move the lever to D, which engages overdrive. I know it's overdrive based on RPM at 60 MPH (versus RPM in 3rd at 60 MPH).

The A340F has 2 solenoids. Here's a chart:




Thanks for the manual!

 

I had to go out to verify using my Ethos Edge on my 98 Tacoma... there is a check for brake switch testing on this scanner. Your scanner might not be sophisticated enough, is there a "live data" feature in the scanner you are using. Like GearCruncher said, the torque convertor wont lock up or go into OD if the PCM senses that the brakes are on via the brake switch. Hopefully it is something as simple as this.

 

You might be on to something here. My ABS light has been on, but I've been ignoring it while I try to find a replacement decel sensor. But the ABS is also throwing a code 49, which points to the brake light circuit. Sounds like I should replace the brake light switch, and maybe that will solve both issues.

 

Or at least check the wiring to and from the brake switch .
I am going $50 bucks thats your issue and has been for the past 2 years .
Thanks for showing the solenoid application chart . I am so use to helping with the 2nd gen trucks with the 5 speed auto , I forget that the 4 speed trans works opposite

 

Update: Replaced the brake switch, but still same behavior. ABS still complaining too. I think there is a problem in the brake circuit, because I can no longer reset the ABS system by tapping the brakes 8 times in 3 seconds with the DTC jumper in place. That used to work for me. Damn.

 

And to clarify, the brake lights are all working fine. The cruise control will engage, and cancels when the brake is depressed.

 

Okay, final update of the day. Time to watch some football. I figured out the braking sequence to reset my ABS system. Took it for a drive; ABS light came back on, and code 49 (stoplight circuit) is back. I saw another thread about replacing all the brake bulbs and ensuring the sockets are clean, so I will try that next.

 

Your truck is going to get really good on fuel once you figure this out .
I beleive 1999 was the first year Toyota went to the abs system for vehicle speed and transmission control . I understand the speedometer runs your dash and instrument cluster but I think the ecm uses the abs wheel sensors for the overdrive circuit as well as the lock up converter circuit . If the ecm thinks you have the brakes applied .....no overdive or converter clutch lock up for you !
Enjoy the game .
Keep us up to date when you get back to this

 

damn... I was hoping that a $20 brake light switch would fix it. That would have been sweet.

 

Thank you all for your help. I'll keep you posted.

 

What was the verdict ? My truck is doing the same now —-