Hey guys just trying to diagnose this issue I have tried a lot and the check engine light and D4 are blinking, the code PO708 keeps coming up and the car will go in first when cleared and dump to fourth gear and then all I have is 4th and 2nd. I have replaced all the shift solenoids and still can’t figure out the issue. Any help would be appreciated.

 

Please let us know the year, trim, engine (4 or 6 cyl), etc.

 

2002 Honda Accord SE 4cyl

 

I don't see a P0708 in the shop manual. Can you recheck the code?

Also, for searching the web for your specific code, P is the only letter. 0708 are numbers. Using the letter o, like PO708 might limit your search results.

 

Sorry it was po780

 

The P0780 means the engine/trans computer (PCM) is indirectly detecting a hydraulic fault in the transmission. The PCM doesn't directly measure hydraulic pressure, so I'll guess the ratio/rate of the shafts spinning is out of spec. This cauld be from a solenoid/valve not opening/closing completely or a hydraulic fault like a clogged valve filter/dirty transmission fluid.

I'll suggest getting the shop manual for your car. You can get a pdf from automanualsource.com for ~$22 and worth the investment. The P0780 procedure is to replace the shift solenoids A/B and the clutch valves A/B. Sounds like you already did the shift solenoids. Have you pulled the clutch valves to at least clean and/or replace?

Also, have you replaced the transmission fluid? Did you use Honda ATF or an aftermarket fluid desigend for Hondas? The recommended fluid change is draining the trans pan (holds ~3 qts), refill with 3 qts, drive to mix, then repeat two more times. So 3 quarts x 3 cycles is 9 qts of fluid replaces most of the old fluid with fresh.

Overall, cleaning or replacing the solenoids and valves then doing a transmission fluid change might not solve the problem, where some other hydraulic fault is happening. That means the transmission needs replaced/rebuilt. The cost of fluid and solenoids/valves is much lower in cost vs replacing/rebuilding the transmission.