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Discussion Starter · #1 ·
Few months ago my AE112 Corolla started to have difficulty staying in overdrive gear, it took me a while to make sure that every sensor that can be involved is working correctly, replaced the transmission fluid anyway, the old fluid wasn't too dark or smelly, also checked tv cable and TPS sensor are set correctly, it has been getting worse until it had become rare when it will engage the overdrive gear and when that happens it's only for a few seconds then back to 3rd gear or switch between 3rd, overdrive and lockup continuously.
I moved my attention to the gearbox internals, I started with the overdrive solenoid, back probed its plug on the transmission case and tested with ohmmeter, resistance is 16 Ohm which is OK, also it's getting 12v until the car warms up then 0 volts, which sounds normal I believe, disconnected the plug completely and took it for a test drive but still no overdrive, then I supplied 12v externally to the solenoid plug and I hear no clicking at all, I was thinking of replacing it but due to that part rarity I thought about deleting the solenoid, my question is does anyone know whether this solenoid is normally closed or open when it's not receiving power?
Any help will be appreciated. Thanks
 

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Broad brush answer from a manual transmission guy....
"a solenoid that is not receiving power is closed in its normal position."

I've dealt with these guys in the past with no issues and they'll ship Internationally.
 

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If your coolant isn't getting hot enough it may not go into overdrive. I know the A245E works this way which is all electronic. On the A240L the only electronic solenoid is the overdrive solenoid, and I'd guess it works the same. So, the first thing you should check is your coolant temperature. Maybe your thermostat is stuck slightly open.
 

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Discussion Starter · #4 ·
If your coolant isn't getting hot enough it may not go into overdrive. I know the A245E works this way which is all electronic. On the A240L the only electronic solenoid is the overdrive solenoid, and I'd guess it works the same. So, the first thing you should check is your coolant temperature. Maybe your thermostat is stuck slightly open.
This is one of the first things I've checked, both the thermostat with the rubber seal were replaced 3 years ago with genuine parts from a Toyota dealership, the original rubber seal was just stretched and was letting the engine run cooler than supposed but I replaced both parts anyway.
I have forced the cooling fan to run continuously while the engine is running inside my garage and monitored the temp with an infrared thermometer, it doesn't go lower than 82C, also the cluster temp gauge stays steady in the middle under all driving conditions.
Not hearing the solenoid clicking at all when applying 12v to its terminals is why I'm targeting it next.
 

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Discussion Starter · #5 ·
Broad brush answer from a manual transmission guy....
"a solenoid that is not receiving power is closed in its normal position."
In this case it seems that the valve is stuck open, would applying 12v in reversed polarity damage the solenoid? just thinking this might help it close back.
 

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I think you're on the right track. Does your O/D off light work when you switch the button from on to off? This will tell you the bulb and switch are working. The repair manual says the solenoid should have 11-15 Ohms when you probe it when it's disconnected. Then when you apply 12 volts directly to it "confirm that a solenoid operation sound is heard." If not, replace the solenoid. In your case it does sound like the solenoid is not working.

I don't think the polarity should matter, because it's (probably) just producing a magnetic field and pulling in a metal rod. It's probably not pulling/pushing a magnet where the direction of the magnetic field matters. And reversing the polarity when you applied 12 volts wouldn't fry it.

Then there are some voltages listed for 4 terminals on the ECU that are related to the A240L O/D Cut System under various conditions (throttle fully open/closed, water temp 20°C/80°C, water temp more/less than 55°C, speed sensor signal). Sounds like you may have already checked these.
 
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Discussion Starter · #7 · (Edited)
Thanks @DrZ for such info, I've checked all the 4 inputs involved and they were within range, the overdrive switch works as it should, it always downshifts to 3rd and OD light turns on when I press that button, also I've lifted both front wheels, shifted into D and watched the speed and rpm climb while a voltmeter is back probed to the solenoid plug, it reads 12 volts until the engine warms up then 0v thereafter, if I lightly press the accelerator I'm sure it engages the overdrive and stays there even on idle, it downshifts to 3rd by slowing down using the brakes.
There's one new thing I've just noticed while driving at freeway speeds, I can almost force it go in overdrive and lockup the torque convertor clutch every time by hard acceleration (more than 50% throttle), if I lift my foot to maintain speed it unlocks the torque converter, RPM climbs to around 3000 and eventually downshifts to 3rd and it stays there on coasting or light acceleration until randomly it would upshift again, can that indicate an issue with the solenoid where increased line pressure overcomes it when the throttle valve cable is pulled? I started to think that it may be burned clutch but then it would never engage on hard acceleration I guess.
I've ordered a transmission pan gasket in preparation for removing that solenoid soon, just wanted to plan ahead what should I do if I couldn't repair or clean it to work again, removing or blocking it might be a good idea, just need to find out whether it is supposed to be closed or open when no voltage is applied.
 

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I have the 3-speed automatic with no overdrive, and last year my lock-up torque converter stopped working, and I haven't figured out why yet.Our situations are a little different because it seems yours doesn't actually shift into the highest gear, and that could be why yours doesn't ever lock-up the torque converter. My only hope is if there is a problem with the governor pressure, otherwise I guess my torque converter is bad. I only drive this car short distances now, so I can live with it like this.

 
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Discussion Starter · #9 ·
My only hope is if there is a problem with the governor pressure
Just a thought, wouldn’t at least the shift points be wrong if the governor is bad?
In my case all the shift points haven’t changed since it was working well except for the overdrive, it sometimes up shifts to overdrive and locks torque converter if I pressed the accelerator hard, then soon it unlocks and usually downshifts while coasting at freeway speeds, removing the governor seems to be easy on the A240L, have you removed the one on yours 3 speed to check it?
 

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I'm not sure if all the shift points would be wrong. Mine takes a little longer to shift into 3rd, but the shift to 2nd seems normal, except one time when I had just started the engine cold and started driving right away. I need to remove the left drive shaft to take the governor out. I'm not sure if that's considered easy. It's should be easy after the drive shaft is out. There is also a way to hook a pressure gauge up somewhere near the governor, but I haven't looked into exactly how to do that or what sized connector I need. With a pressure gauge you can test the governor pressure. It's not a high priority for me right now since I only use this car as a backup and it passed emissions a month ago for the next 2 years and it's getting above 100°F (38°C) here and will be a little hotter for the next 3-4 months.

In your case, it sounds like the solenoid could very well explain your symptoms, and it's relatively simple to take out and check.
 
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