What does it mean?
P1764 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Shift Solenoid C Short Circuit Continuity-Disconnection .
Symptoms
- MIL (check engine lamp) is on and the transmission drops into limp mode, usually holding one fixed gear
- One or more gears are missing; the gear the module commands is not the one engaged
- Harsh, banging shifts or engine flare between gears
- Reverse may be weak or unavailable on some units
- High engine speed at cruise and noticeably worse fuel consumption
- No kickdown when the pedal is floored
Likely causes
- Shift solenoid C itself failed: winding open, shorted between turns, or resistance well outside specification
- Wiring inside the transmission chafed against the case or valve body, shorting the solenoid drive wire to ground
- Corroded or fluid-contaminated pins in the transmission case connector, giving intermittent continuity
- Short to battery positive on the solenoid control wire where the external harness runs near hot feeds
- Metal debris or varnish in the solenoid bore, jamming the spool and driving current out of range
- Backed-out or spread terminal at the TCM connector
- Failed solenoid driver stage inside the TCM (least likely, check last)
How to fix it
- Record freeze frame data: fluid temperature, road speed and commanded gear at the moment of the fault
- Check transmission fluid level and condition; dark fluid with a burnt smell or metal glitter changes the whole diagnosis
- Inspect the case connector and the harness where it passes the bellhousing for rub-through, then wiggle-test while watching live data
- Measure shift solenoid C winding resistance at the case connector and compare with specification; also check for a short to case ground
- With the solenoid unplugged, check the TCM-to-solenoid wire for continuity and for shorts to ground and to battery
- Command the solenoid on and off with a bi-directional scan tool and watch commanded versus actual current
- Replace the solenoid or valve body if it is out of specification, and service the fluid and filter if contamination is found