What does it mean?
P1822 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Internal Mode Switch 'B' Circuit Low Input (4T80-E) .
Symptoms
- Check engine lamp on with a wrong or missing gear position display
- The transmission defaults to a fixed gear and pulls away in it
- Cranking allowed in the wrong range, or no crank at all
- Late or absent reverse engagement
- Harsh shifts, limp mode and generally poor drivability
Likely causes
- Internal harness rubbed through against the valve body or case, grounding the B circuit
- Contact track inside the mode switch worn or pitted so it stays closed to ground
- Fluid tracking between pins in the internal connector after a seal has hardened
- Mode switch not aligned to the manual shaft after service, leaving two tracks overlapping
- Corroded or bent terminal in the external case connector
- Mode switch assembly failed internally
- Module input circuit damaged by a long-standing short to ground
How to fix it
- Read the codes and watch all mode switch states while the selector is moved slowly through every detent
- Inspect the external case connector for fluid, corrosion and terminal tension
- Disconnect the switch and test circuit B for a short to ground back to the module
- If the external wiring is clean, remove the pan and inspect the internal harness for rub-through and the connector for fluid tracking
- Confirm switch alignment to the manual shaft before condemning the assembly
- Renew the mode switch and, where damaged, the internal harness
- Clear codes, sweep the selector through all ranges and verify the reported states are now valid