What does it mean?
P1864 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: TCC Solenoid Electrical .
Symptoms
- Malfunction indicator lamp on with a torque converter clutch code stored
- No converter lockup, so engine rpm sits higher than normal at cruising speed
- Fuel economy drops noticeably on the highway
- Shift feel may become harsh because the module reverts to a default strategy
- Transmission fluid temperature rises faster than usual
- Vehicle may be limited to one or two gears until the fault is cleared
Likely causes
- Open circuit or high resistance in the TCC solenoid feed or control wire
- Solenoid winding open or shorted internally
- Corroded, spread or oil-wetted terminals at the transmission case connector
- Leaking case connector seal letting fluid wick up into the harness
- Debris in the solenoid holding the plunger and changing current draw
- Broken internal harness wire where it flexes near the valve body
- Failed solenoid driver circuit in the TCM/PCM
How to fix it
- Check the transmission fluid level, colour and smell before any electrical work
- Read the freeze frame data and note vehicle speed and fluid temperature when the code set
- Disconnect the case connector and measure the solenoid winding resistance against specification
- Check the feed side for battery voltage and the control side for a good path to the module
- Command the solenoid on and off with a bidirectional scan tool and watch the current or listen for actuation
- Repair corroded terminals or replace the internal harness if fluid has wicked into it
- Replace the solenoid, then reassess; only replace the module once wiring and solenoid test good