What does it mean?
P1773 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Lockup Solenoid Valve 'B' Circuit Malfunction .
Symptoms
- MIL (check engine lamp) is on and the converter clutch never locks up
- Engine speed stays several hundred rpm higher than normal at steady highway speed
- Noticeably worse fuel consumption on long runs
- Shudder or vibration around light-throttle cruise, as if driving over rumble strips
- If the solenoid sticks applied, the engine stalls or nearly stalls when coming to a stop
- Transmission fluid runs hotter than normal
Likely causes
- Lockup solenoid B winding open or shorted, resistance away from the specified value
- Short to ground or to battery on the solenoid control wire in the engine bay section of the harness
- Corroded case connector where transmission fluid has crept into the terminals
- Sticking solenoid valve caused by varnish or clutch material in the hydraulic circuit
- Worn torque converter clutch lining or a leaking converter, so the module never sees lockup achieved
- Contaminated fluid or a clogged filter starving the lockup circuit
- Failed lockup driver output in the control module
How to fix it
- Check the fluid level and condition first, since lockup faults quickly cook the fluid
- On a road test, watch converter slip rpm in live data and note whether commanded lockup ever reduces it
- Measure lockup solenoid B resistance at the case connector and compare with the specified value
- Check the wire from the control module to the solenoid for continuity and for shorts to ground and battery
- Command lockup on and off with a scan tool at a steady speed and observe engine speed response
- Replace the solenoid or valve body if the electrical value is wrong; if the electrical side is good and slip stays high, the converter itself needs attention