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Thread: Overdrive issues

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    Overdrive issues

    I'm having problems with it kicking into overdrive and I talked to a local toyota mechanic and he said, the thermo is stuck open so the engine is abnormally cold not allowing the temperature sensor to register right, which has to be a certain temperature to allow the overdrive switch engage.

    So I blocked off almost all of the radiator from receiving any air flow and drove pretty far on a decent day (mid 70's), and no change. What does this indicate?

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    Re: Overdrive issues

    That indicates a problem with the overdrive system (not the cooling system). Keep in mind the OD system should engage at 55 deg C (131 deg F) so even a stuck open engine thermostat will allow the van to warm up enough to activate the system. If your heater works correctly (blows hot air) then your coolant temp is definitely above 55 deg C.

    When the van fails to go into overdrive, the 1st thing to do is check the 7.5A fuse in the top center of your fuse box:


    This fuse also supplies power to your gauges and some of your warning lights, so if that stuff works then it's probably not it, but it's easy to check so you should check it anyhow.

    If the fuse checks good take off your center console and inspect all of the wires in this area. Make sure they are all connected securely and free of damage. Note: shorted or grounded wire(s) in this area can prevent your OD from working, so make sure the wires have separation (not pinched together) and make sure the wire insulation is intact with no exposed copper. Pay particular attention to the blue/white wires and the little blue box that sits up in front of the shifter (under the console cover). That box is your overdrive relay (on 2wd vans only). Note: the 4wd van has a slightly different / more complicated OD system, but since yours is a 2wd we'll stick to 2wd for the sake of this discussion.

    Here's the relay used on 2wd vans:


    Here's the harness that goes to the switch:


    Make sure it's hooked up to this plug coming from the shift mechanism. Note: two of the wires inside this black protective tube are the OD switch wires. Since the switch side wires (actual wires coming from the shift lever switch) are subject to change color, always identify them by tracking them up to the shift lever or identify by the wire color on the "van side" of the harness. The colors on the harness are wht/blk & orange. One thing worth noting. The switch does not turn-on the OD (it actually limits it). Electrically speaking, when the switch is closed, the OD will not work and the "O/D OFF" indicator light will illuminate. When the switch is open, the "O/D OFF" light will go out and the van will be free to shift into OD (assuming there are no other issues).



    If the relay and wires in this area are hooked up and look good, then remove the passenger seat, peal back the carpet and remove the big engine access panel (Instructions on how to remove are covered HERE). Once off you will have access to your OD thermo switch.

    Here is it's location:


    The thermo switch is N/C (Normally Closed). When the van is cold (less than 55 deg C) it grounds out the OD circuit preventing the transmission from shifting into OD. Once the coolant temp hits 55C the switch opens and that enables the OD circuit. Because of the way Toyota set it up it's easy to bypass the thermo switch. All you need to do is unplug the gray harness connector to the thermo switch and that's it! If the thermo switch is the problem, then the OD system will now be active.

    If disconnecting the thermo switch doesn't work, then you'll need to check the OD solenoid on the transmission. It's on the drivers side of the tranny here:


    It is grounded through the transmission and is activated by a single wire. Here is where that wire connects to the harness:


    And here is the connector position when installed in the van:


    Before you get involved with testing components make sure the solenoid is in good physical condition and verify it's hooked up to the van wire harness. Trace the wires as far as you can to verify there's no physical damage to them either.

    If you are unable to resolve the problem at this point, let me know and I'll walk you through component level troubleshooting. Tim

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    Re: Overdrive issues

    Question: is the "OD off" indicator on your cluster illuminated? If so that would indicate a shorted switch or shorted wires to the switch. If that's the case then the 1st thing I'd do is disconnect the switch harness (the one shown in pics 3 & 4) and see if the light goes off. If it does, then test drive the van with it disconnected to see if it shifts. Tim

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    Re: Overdrive issues

    I had a 90 4-runner that was doing the same thing. It seemed to get up to temp according to the gage, and my heat was definitely blowing warm. I changed the thermostat and it shifted into overdrive. How high was your temp gage when you blocked the radiator? I just want to confirm that it can happen like your mechanic said. My temp gage after the thermostat change was went from about 4/5ths to half way up.

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    Re: Overdrive issues

    I'm not sure what temp the 4 runner ODs are supposed to kick in, but suspect they would be the same as the van. 131 deg F isn't very hot (heater would only blow warm). Perhaps your thermo switch was messed up??? By messed up I mean off a bit (like maybe it wasn't kicking in until 180 deg or so). The t-stat on my work van got stuck open and I drove it for almost a year before replacing it. OD would always kick in by the 2nd mile after a cold start. Tim

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    Re: Overdrive issues

    Ok, great post. Thanks a lot.

    I just checked the fuse, it was ok. So then I checked the relay wires and relay itself for continuity and it is ok as well.

    As the other things are a bit more involved I'll probably wait till I have more time to get into it. But I'm looking forward to going faster than 55 mph!

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    Re: Overdrive issues

    While odds are that Tim is right and its not your thermostat, I would still start there if I were you. Its really a lot easier than it looks. Just make sure you have a long extension for your socket. I have a 6 inch extension for the 1/4 inch drive that worked great. I think it took me about 30 to 45 minutes, although I already had the fan shroud out of the way. Even still, its not that bad, and you'll eliminate that as a possibility and have a van that runs more efficiently. Good luck!

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    Re: Overdrive issues

    Question: is the "OD off" indicator on your cluster illuminated? If so that would indicate a shorted switch or shorted wires to the switch. If that's the case then the 1st thing I'd do is disconnect the switch harness (the one shown in pics 3 & 4) and see if the light goes off. If it does, then test drive the van with it disconnected to see if it shifts. Tim
    No, regardless of whether or not how much i press the switch; no indication on the dash. I checked the fuse, where else to check? I think I'm gonna start with the thermostat first though.

    And even after I blocked my radiator there was no change even after a 30 miles trip. So I don't know what that's about.

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    Re: Overdrive issues

    No OD light either way does not sound good at all. Out of curiosity, have you tried hitting the switch while driving fast enough that is should shift to make sure that you don't have it the wrong way? More likely, though, something's not connected properly and that's your problem. That's Tim's department. I would follow his instructions to identify where the problem is.

    Has your overdrive ever worked? You may want to make sure that the wiring clip that goes into the front of the shifter is actually connected. If memory serves me correctly, I drove my van once without reconnecting it and I think I remember that it wouldn't shift into overdrive for me either. I do remember for sure that obviously the OD light would not change when I hit the button because the wiring clip was disconnected. I think the light was off, but I'm not positive about that.

    Good luck!

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    Re: Overdrive issues

    Sorry, I just realized my advice about making sure your clip is connected is exactly what Tim already said to do. It's definitely your first step though.

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    Re: Overdrive issues

    I've only had the van for about 2 weeks and the OD has never worked. I got it going about 50 the other day and hit the switch and nothing happened. The light has never worked either. The harness and relay is connected and working just fine.

    But that light not coming on has stumped me. If the light is off it should be in OD, which would be fine. But it's not, and no matter how long I drive, how fast I'm going, how hot the engine is, and how many times I press the switch; no change.

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    Re: Overdrive issues

    Have you taken the engine cover off and disconnected the thermo switch? This is a very simple circuit so there's only a few things that can go wrong. Tim

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    Re: Overdrive issues

    Not yet Tim, I just disconnected the transmission relay while driving and no change. And also double checked the wires, all's good.

    I haven't disconnected the thermo switch yet, it's been raining here. And I plan on insulating under the seats, and would like to do it all at once.

    For now it's rock climbing and drinking.

    I'll keep ya'll posted.

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    Re: Overdrive issues

    Disconnecting the relay won't help (that would insure the OD won't work). I was talking about the harness connection to the switch. When you get the engine cover off check the harness connection that goes to the solenoid. Disconnect it and verify the conductors inside are clean and shiny. After you've done this simple stuff, if you still get no joy, post again and I'll walk you through more advanced testing. Tim

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    Re: Overdrive issues

    I disconnected the temp sensor and no change. It did not shift in to overdrive. The plug was pretty dirty and so was the whole engine actually. So I guess I check the solenoid now.
    Last edited by llamavan; 11-01-2018 at 05:19 PM. Reason: removed off-topic remarks

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    Re: Overdrive issues

    The plug I'm pretty sure is the temp sensor plug.



    Last edited by llamavan; 11-01-2018 at 05:19 PM. Reason: removed off-topic remarks

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    Talking Re: Overdrive issues

    Eureka! Last night going to a pub I noticed I was going 60 mph and my engine wasn't stressing out! IT SHIFTED INTO O/D!!!

    I'm so effin excited!!! Weird thing is...now I can press the O/D switch and it will kick out of O/D, but there is no indication on the dash? Maybe the light is out? But I thought since I disconnected the temp switch it wasn't able to shift in and out of O/D?

    I don't really want to look a gift horse in the mouth, but I'm just curious. I CAN DRIVE 55mph, and then some! YEAAAHHHHHHHHHH!!!!!

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    Re: Overdrive issues

    I thought it wasn't able to shift in and out of OD even before you disconnected the temp switch. Not really sure what you're asking but I'm happy it's working. Just don't touch anything......seriously! don't even breath hard . Tim

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    Re: Overdrive issues

    Quote Originally Posted by timsrv View Post
    I thought it wasn't able to shift in and out of OD even before you disconnected the temp switch. Not really sure what you're asking but I'm happy it's working. Just don't touch anything......seriously! don't even breath hard . Tim
    x2.

    Unless you are in an extremely cold climate you can leave the od temp switch unplugged. the system is designed to keep you from "bogging" your engine when it's really really cold to prevent blow-by gasses from entering the crankcase and more importantly to speed up the warm-up cycle and promote cleaner combustion (emissions.... damn smog hippies).

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    Re: Overdrive issues

    That's what I'm saying!!! But there is so much more work I have to do!!!

    Replace the thermostat
    Rebuild the p/s pump and res
    Change spark plugs and ign wires

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