2004 Honda Odyssey 150k with P0740, P0706, P0705 Codes - How to Fix Without Flushing? | TCS Light Fluctuates
I recently purchased a 2004 Honda Odyssey with 150,000 miles. It runs smoothly and has no noticeable shifting issues, but the check engine light is on and it's throwing diagnostic codes P0740, P07006, and P0705. Additionally, the TCS (Traction Control System) light comes on and off frequently while driving on flat, dry pavement. I bought this vehicle from a friend who reportedly had no intention of hiding major issues. While it runs well, I’ve just learned that these codes are likely preventing me from passing state inspection. As a single disabled woman with a fixed and extremely low income, I cannot afford unexpected breakdowns or expensive repairs—especially after I recently emptied my bank account to buy the car. I plan to drive only about 5,000 miles per year (and possibly less), with occasional cargo loads that may increase weight. The seller mentioned that a transmission fluid flush might resolve the check engine light issue, but he said he didn’t want to do it since he was selling the vehicle. The current fluid appears ruby-colored and not visibly dirty—so I’m unsure if a change is needed. However, I’ve only had the car for a few days, so I don’t yet know what normal shifting behavior should look like. I’ve read that older 2004 Honda Odysseys are prone to transmission-related issues, and some reports suggest that fluid flushes or improper fluid types may actually accelerate transmission failure. My main questions are: - Will a DIY transmission fluid change (without a professional flush) fix the P0740, P0706, and P0705 codes? - If so, what brand of fluid and filter would be recommended for this model? - Should I go with a DIY 3x1 or 3x3 fluid change instead of a professional flush? Additionally, are there any troubleshooting steps I can take to diagnose the issue before investing in repairs? And if changing/flushing isn’t advised right now, what’s the best way to clear these codes for inspection purposes and how can I extend the life of this vehicle? Thanks for your advice—any insights would be greatly appreciated. Dee in Texas
Avoid performing a fluid flush or change at this time. The P0740, P0706, and P0705 codes point to wiring faults in the transmission control circuits—specifically the Torque Converter Clutch (TCC) and Transmission Range Switch. These issues are typically mechanical or electrical, not fluid-related. A professional diagnosis from a reputable transmission specialist or dealership is recommended before any fluid work. DIY changes could worsen the problem or lead to further damage if the underlying wiring or sensor faults aren't addressed first.