P0766 means Shift Solenoid D Performance or Stuck Off. The computer commanded shift solenoid D, but the gear change it expected did not happen, so the solenoid or the valve it controls is not working as commanded. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0766 means
Electronically controlled automatics are run by a transmission control module (TCM), a separate box or part of the engine computer. It reads speed sensors, the range sensor and fluid temperature to decide when to shift, and drives solenoids that apply clutches and the torque converter clutch. Many basic code readers only show the generic P0700; a scan tool that reads the transmission module shows the specific fault. Check fluid level and condition first, since low or burnt fluid causes many transmission codes.
P0766 symptoms
- Stuck in one gear or limp mode
- Missing gears or late, harsh shifts
- Engine speed flaring between gears
Common causes of P0766
- Sticking solenoid from debris or degraded fluid
- Low fluid level
- Sticking shift valve in the valve body
- Wiring or connector faults in the solenoid circuit
How to diagnose P0766
- Check transmission fluid level and condition first
- Check for metal or friction debris in the pan
- Command the solenoid with a bidirectional scan tool and watch for the gear change
- Check solenoid resistance at the case connector
Can you drive with P0766?
Only as needed; repeated harsh or slipping shifts wear clutches quickly.
P0766 tips
On many six-speed and newer automatics, solenoids C and D control specific clutches. Performance codes with debris in the pan point to internal wear rather than the solenoid.
Will P0766 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0766 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0750 | Shift Solenoid A Malfunction |
| P0753 | Shift Solenoid A Electrical |
| P0730 | Incorrect Gear Ratio |
Guides that help
When it is more than a sensor
If the fault turns out to be internal (worn clutches, a failed converter or a damaged valve body), compare a rebuild with a replacement in transmission rebuild vs replacement and transmission replacement cost, identify your unit with what transmission do I have?, and browse our transmissions.
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