What does it mean?
P1841 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Transmission Fluid Pressure Sensor/Switch B Circuit .
Symptoms
- Check engine lamp on and a transmission message on the cluster
- Shifts that are harsh in one range and soft in another
- Occasional slipping and flare on a particular gear change
- Torque converter clutch dropping out at cruise
- Limp mode, single-gear operation and poor drivability
Likely causes
- Switch contacts stuck by varnish, clutch material or fine debris in the fluid
- Open or shorted wire in the B circuit between the switch and the module
- Corroded terminals or fluid wicking in the transmission case connector
- Internal harness chafed against the valve body or a pan magnet
- Sticking valve body spool so pressure never reaches that circuit
- Failed pressure switch assembly with an internally shorted track
- Module input circuit damage after a long-standing short
How to fix it
- Read all stored codes; several pressure switch codes together usually mean fluid contamination rather than several failed switches
- Check fluid level and condition, and look for debris on the pan magnet
- Inspect the case connector and external harness for fluid, corrosion and chafe
- Test the B circuit for continuity and for shorts to ground or voltage with the switch disconnected
- Watch the switch state live while driving through the ranges where it should change
- Fit a line pressure gauge and verify the actual hydraulic condition
- Replace the pressure switch assembly and clean or renew the valve body where debris is found, then retest