What does it mean?
P1776 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Torque Converter Clutch Solenoid Circuit High Input .
Symptoms
- MIL (check engine lamp) is on and the torque converter clutch never engages
- High engine speed at motorway cruise and a noticeable jump in fuel use
- The vehicle feels as though it is always slipping slightly at steady throttle
- Transmission fluid temperature rises on long journeys
- Possible limp mode with a fixed gear
- Fault may appear only when hot, then clear after cooling
Likely causes
- Open circuit in the solenoid control wire between the control module and the transmission
- Solenoid winding open, giving infinite resistance at the case connector
- Terminal backed out, corroded or pushed in at the case connector or module connector
- Short to battery voltage on the control wire, holding the circuit high
- Blown fuse or open relay contact in the solenoid supply feed
- Poor connection at a previous harness repair or an intermittently open splice
- Control module driver stuck open
How to fix it
- Check the fluid level and condition, then read the freeze frame data
- Measure solenoid resistance at the case connector; an open reading confirms the solenoid or its internal wiring
- Check continuity of the control wire from the module connector to the case connector with both ends disconnected
- Test the same wire for a short to battery voltage with the ignition on
- Verify the solenoid supply fuse and relay output, since a lost supply also reads high
- Inspect both connectors for backed-out and corroded terminals, repair as needed, then confirm lockup engages on a road test