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I have a 2005 Honda Civic and live in Minnesota. When the temperature drops in the winter, after the car drives for 10 minutes or so on a very cold day it will downshift on the freeway and I need to pull over, turn it off, wait a few minutes, and start it up again before I can drive it in a higher gear. It only happens once a day. 3 years ago we had the throttle body assembly replaced, and that worked initially and then the same symptoms started after a year, so we replaced it again, which was still covered by the warranty. But now after another year it is happening again, and replacing the assembly will cost another $600. What else might be causing this problem???? Thank you. 🙁
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Strange that it downshifts OUT of overdrive, most newer cars won’t shift into OD at all until they reach a certain temperature. Supposedly to help warm the car faster on cold days or something like that.
I wonder if you have an overly sensitive engine coolant temperature sensor (not the sensor for the gauge), when the thermostat opens a rush of cold coolant from the radiator hits the sensor and then it tells the computer the car is too cold again and the ECU locks out OD. While you are on the side of the road the heat from the engine brings all that cold coolant up to temp so it functions normally when you start out again.
I’m just guessing this from some stuff I read online about CR-V owners having similar problems with OD and cold days. Some mention the thermostat itself, they replaced and the trans shifted normally thereafter. Not sure if any of that translates into the same problem in a Civic though.Only other thing I can think of is the TPS sensor, my mom’s Ford Escort had the TPS go bad but instead of losing OD it instead shifted back and forth between 3rd and OD constantly but a Honda may react differently.
One question, are you sure it’s actually downshifting and not just losing the torque converter lockup? Could be that lockup is having an issue.
Since TB replacements seem to cure the problem for a year at a time, could be the TPS/connector/wiring becoming intermittent in cold.
If PCM loses track of the TPS signal likely the engine will go into limp home mode( transmission locks in a lower gear.)
Shutting off/ restarting engine apparently resets error.Is there a check engine light or error code when the problem happens?
A 600$ repair must have been the TB including IAC/TPS.
It could well be that the entire TB doesn’t need replacing, if you can get a more accurate diagnosis.If OP’s car went into limp mode, they would know.
As u/Nodak81 suggested, is it only locking you out of overdrive? Or is it limiting you to a gear below 3rd? I live north of Minnesota and have never heard of this happening, even spent a year at a Honda dealer so I’m skeptical about the cold itself causing the issue.
You should try and accurately record the series of events and details leading up to and including when the failure happens. Problems like this can be very difficult to recreate when incomplete or insufficient information is provided. Obviously if replacing the throttle body only temporarily cured the problem, it is not the root cause.
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