I own a 2004 Honda Civic EX 1.7 automatic transmission. 168,648 miles. Code P0730. 1st and 2nd gears are strong but at the time to apply 3rd start slipping and going to neutral. If force check engine light comes on with P0730 and goes to some kind of safe mode and stays in 1st gear. Trans is making a humbing noise (like a power steering without oil). Oil level and condition is good. Also check the celenoids not clog and working. Thinking that the torque converter is gone. Thanks in advance for your answer.
You can try the Lucas additive https://www.autozone.com/motor-oil-and-transmission-fluid/transmission-additive/lucas-oil-products-trans-fix-24oz/202087_0_0
It doesn't always work but it's worth a shot. Otherwise 3 gear is starting to go and your going to need another transmission before too long. Don't get it rebuilt Scotty has said many time no one knows how to rebuild them. Best option is to try and find a good used one from a junk yard car.
Hello,
Here are some possible causes of P0730,
I would change the gearbox oil and filter first, But be advised this could make the problem worse.
https://www.autocodes.com/p0730_honda.html
All the Best.
@dvkala
If I'm not wrong, this transmission has an internal filter. The only way to change it its by taking it apart.