P0788 Transmission System Problem

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pennystocks

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Has anyone ever had this issue? Was presented with Transmission System Problem on dash and OBD reports P0788 Shift Solenoid High. Guessing a Solenoid is stuck open. The car sat for 2 weeks during a Texas "deep freeze", temps around 0-20 degrees over night. Car drives fine in EV. Can't change drive modes or go into HV. The engine will start up if going past the bump on the pedal tho and seems to work fine. I feel like its something do with the direct drive for the engine. Burning the battery down now with the heater to force it into HV mode (rather do this than maintenance mode) to drive it with the engine on and warm it up but I'm guessing it's going to drive without direct drive and run in charge mode at higher speeds. The P/N/R/D indicator on dash also flickers/flips.



Anyone had this issue? Hopefully it'll fix itself once it warms up. It's about time for a transmission fluid change so maybe I'll look into that. Online says low or dirty fluid can cause this code with solenoids.

OBD.webp Dash.webp
 
Further investigating going to buy a Solenoid Assembly B - Honda (28460-RT4-003), replace it and do a transmission fluid change. Hoping it's just the cheap solenoid that's bad and not electrical issue.
 
Animal must have chewed through the wire! It was weird it looked like a clear cut, you can see the cut in the wire wrap and it was clean cut, no chewed up bits. No idea, it was running fine until parked for 2 weeks so had to have happened when sitting. Either way, soldered the little bit that was left then heat shrink, not much to work with but engine code went away. The positive wire had a little gash in it too but wasn't cut. I'll probably buy a new connector with more wire and resolder with more surface area. No way I'm going to replace the whole harness, I can't imagine how much it would cost. Car is 5 years old, 2018 and 85k miles and will be driven until it's a backup car or dies, not worth a proper fix IMO.





Wire1.webp Wire2.webp
 
Or perhaps road debris that was thrown up on last trip (would explain clear cut and no other damage) and computer didn't sense it until a restart.
 
I have heard that the dealers are prohibited from repairing wires in a harness like this.
They are required to replace the entire harness (which can be an extreme job).
To me, this is an idiotic policy.

You will have a repair that is just as good as it was originally and at a trivial cost.

I have had multiple occurrences of rodent damage over the years in other vehicles, and I can tell you that it is not unusual for it to look like the wire was cut. Their little teeth must be razor sharp.

You may want to check your cabin filter... It is well known that that is where the little critters like to build homes, and during that 2 week period, they are likely to have set up shop !

Excellent job at sleuthing this out and repairing it ! Thanks for sharing your experience.
 
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