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Discussion Starter · #1 ·
I have Honda Pilot 2003 with 270 thousand miles. Now had Transmission problem and I found out it work fine when Transmission temperature below 130F but as soon as increase more than it start failed to shift to 3rd gear and always got error p0780. So as last resort I am thinking lower temperature on Engine. Currently average temperature of engine 182F. Actually I did make one modification and before that if idle temperature can raise to 205 F which at the time the fan will blowing if AC not running. The modification I made is to use bayite DC 12V Fahrenheit Digital Temperature Controller 10A 1 Relay with Sensor which I install the temperature sensor close to coolant temperature sensor. The temperature detected will be around 30F lower than coolant temperature so I calibrate adding 9F and I set the fan will turn on at 165F which will turn on the fan at 180F WTF. Maybe my thermostat is bad because the fan switch A even after I replace will never activate the fan at 195F because the temperature at switch is around 20F below coolant temperature sensor. SO I am thinking lower the engine temperature by using thermostat which will active 10C below standard activation temperature 78C. So I tried to find thermostat that will activate at 68C instead of 78C but I want the good quality like AISIN. I also will install Transmission Cooler Hayden 769 and Power steering cooler Hayden 402 (It actually smaller Transmission cooler). I wish I knew the problem of Pilot transmission long time so I will install Transmission cooler when I bought used around 90k miles. But now at least after install transmission cooler it still had problem I will give up. Did anyone ever use lower temperature thermostat in Honda Pilot 1st Gen?
 

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I splurged for the $$ OEM thermostat so I can’t answer your question but maybe a large ATF cooler separate from the engine cooling system with its own electric fan thermostatically controlled for the transmission temperature you desire.
 

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I think that P0780 is the generic "transmission problem" code, which isn't telling you anything you don't already know.

You need to get the specific code from a reader that understands Honda transmissions. That will tell you where your real problem is. Addressing that will probably be easier than trying to manipulate the ATF temp. It might be something easy, like a faulty solenoid.
 

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it start failed to shift to 3rd gear
Change out the 3rd (and 4th) gear pressure switches. That solution has been found to help in several instances. Get OEM only.
 

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Discussion Starter · #5 ·
Change out the 3rd (and 4th) gear pressure switches. That solution has been found to help in several instances. Get OEM only.
I did that already and also replaced all solenoid. The one I didn't replace yet Input and output VSS.
 

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Discussion Starter · #6 ·
I think that P0780 is the generic "transmission problem" code, which isn't telling you anything you don't already know.

You need to get the specific code from a reader that understands Honda transmissions. That will tell you where your real problem is. Addressing that will probably be easier than trying to manipulate the ATF temp. It might be something easy, like a faulty solenoid.
I did replace all solenoid and using honda trick to read DTC it gave code 45-1 which actually p0780 using OBD scanner
 

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2008 Piot SE FWD, 2015 Pilot LX 4WD. 2005 GSX-R1000
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You didn't say, or at least I didn't read; but, have you changed any ATF fluids lately? Did it help?
People around here including me are having great results with the Valvoline Mas Life ATF fluid. It's Synth. and it works well in our transmissions too. I use it on both of our Pilots, both 5 speeds.

Valvoline Maxlife is less than $18/gallon at Walmarts too. Low $$, works great!

If you haven't tried that yet, I recommend 3 x drain and fills on your tranny, with a few minutes driving between.

I feel trying the lower temp route you are trying is not a good way to go about this. IMHO
Good luck.
 
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Discussion Starter · #8 ·
You didn't say, or at least I didn't read; but, have you changed any ATF fluids lately? Did it help?
People around here including me are having great results with the Valvoline Mas Life ATF fluid. It's Synth. and it works well in our transmissions too. I use it on both of our Pilots, both 5 speeds.

Valvoline Maxlife is less than $18/gallon at Walmarts too. Low $$, works great!

If you haven't tried that yet, I recommend 3 x drain and fills on your tranny, with a few minutes driving between.

I feel trying the lower temp route you are trying is not a good way to go about this. IMHO
Good luck.
I did read many post from this site about transmission problem so first time I did flush 3 times using Max Valvoline ATF. Then replace solenoid and pressure switch. The car work fine when Transmission temperature below 130F which I got using cheap sensor Helonge LCD Digital Thermometer,4 Pcs Fahrenheit Temperature Monitor with Probe for Fridge Aquarium Fish Tank Water Terrarium Vehicle Reptile attached to OEM transmission cooler pipe. I still try to figure out how to read transmission temperature from OBD but look like not possible for Pilot 1st Gen. I have Scan GaugeII but only can get coolant temperature. So I noticed problem start happening when Transmission temperature above 130F I assume and at that time actually coolant temperature stay normal at 182F. It something cause Transmission overheat which I think Torque Converter which maybe already damaged. It could be one of solenoid in transmission not function properly when temperature above 130F. So look like my last resort is to lower transmission temperature using Transmission Cooler.

So whoever read this don't think anymore just install Transmission Cooler even though you will never tow anything because the heat caused transmission or torque converter died even actually I am lucky enough to get transmission problem after 270K miles. Also always change Transmission oil every 30K and install Magnefine oil filter. Also monitor Coolant and Transmission Temperature using OBD or attached custom temperature sensor. Overheat kill engine and transmission. If I don't have this problem maybe I never know that my radiator fan not activated that cause the idle temperature rise to 206F when it activated which I think that too high it should be activated around 185F. If I let overheat for long time soon it damage the gasket and leaking oil.
 

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Discussion Starter · #11 ·
I did replace thermostat with 68C instead of OEM 78C. I got the thermostat from Amazon Mishimoto MMTS-S2K-00L Racing Thermostat. Now average coolant temperature drop from 182F to 160F. There are improvement to prevent transmission problem shift from 2 to 3. The strange thing used to be if transmission temperature150F and coolant 170F it still fine. Before thermostat replaced it already problem when transmission temperature 130F and coolant 182F. So look like the problem more on overheat engine than transmission. I though it could be shift solenoid overheat cause problem because it close to engine body and impacted by engine temperature. But anyway I am installing Hayden Transmission Cooler 579 inline with OEM cooler. Tomorrow I will test and see if I can bring my pilot back to life again without p0780 when it overheat.
 

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Discussion Starter · #12 ·
I did install transmission cooler in addition to OEM cooler. It definitely improve a lot. I drive for 30 minutes and no more p0780. The coolant temperature stay on 170F and actually transmission temperature on OEM cooler is still raising to 130F but it survive limp mode with P0780. I feel transmission slip when temperature of transmission relatively high above 120F. Actually I think I did experienced car jerk when slowing down and sometime it slip to neutral. The next step is to bypass OEM cooler because I think it function more as heater than cooler because the heat of engine and radiator may cause increase of heat in transmission. The problem could be caused by speed sensor not function properly when it overheat which cause jerk off. The problem could be caused by Shift solenoid A and shift solenoid C which not replaced yet with OEM.
 
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