Symptoms

- Engine Light ON (or Service Engine Soon Warning Light) - Transmission will not shift gears.

Possible Causes

- Low transmission fluid level - Dirty transmission fluid - Faulty shift solenoid D valve - Shift solenoid D valve harness is open or shorted - Shift solenoid D valve circuit poor electrical connection

When Detected

The P0766 code is detected when the gear required by the Engine Control Module (ECM) does not match the actual gear when driving

Tech Notes

There is a factory service bulletin for the 2008 Toyota Tundra: 2008 Toyota Tundra Service Bulletin OBDII Code P0766

Description

The Engine Control Module (ECM) uses signals from the output shaft speed sensor and input speed sensor to detect the actual gear position (1st, 2nd, 3rd or O/D gear). Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves, valve body or automatic transaxle (clutch, brake, gear, etc.).