What does it mean?
P1825 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Internal Mode Switch 'P' Circuit Low Input (4T80-E) .
Symptoms
- Check engine lamp on with an incorrect or blank range display
- The engine may crank in a drive range, or refuse to crank in Park
- Delayed or hard engagement when selecting Drive or Reverse
- The unit pulls away in a higher gear than it should
- Limp mode with restricted shifting and poor drivability
Likely causes
- Park wire grounded through a chafed or fluid-soaked internal harness
- Mode switch contact worn so the Park track stays made in adjacent positions
- Fluid intrusion in the internal or external connector bridging pins together
- Switch left out of alignment after valve body or manual shaft work
- Damaged terminal in the case connector shorting to the case
- Mode switch failed internally after high mileage and heat cycling
- Module input circuit damaged by an unrepaired ground short
How to fix it
- Read the codes and log the mode switch states through a slow sweep of every selector position
- Inspect the case connector for fluid wicking, corrosion and loose terminals, and reseat it fully
- Disconnect the switch and test the Park circuit to ground back at the module
- Verify manual shaft and cable adjustment, then check the switch alignment marks
- If external testing is clean, remove the pan and inspect the internal harness and switch connector for chafe and fluid tracking
- Replace the mode switch, and the internal harness where it is damaged
- Clear the codes and confirm every range now reports a valid pattern