In order to actuate a gear change, some transmissions use a metal band lined with friction material to stop a clutch drum from spinning so the gear change can take place. This transmission band is activated by the brake band apply solenoid, which directs pressurized ATF down the right channel to squeeze the transmission band around the drum. If there is an issue with the functionality of this solenoid, a P1851 diagnostic trouble code will be stored in the ECU.
How Serious is the Code?
The P1851 OBDII diagnostic trouble code is quite serious, in that the underlying problem will eventually cause a serious impact on the drivability of your vehicle. Not only will the gears start to slip, but further internal damage will occur.
Symptoms of a P1851 include:
- Slipping between gears
- Delayed shifts
- Erratic transmission behavior
- Burning smell from the transmission
- Transmission overheating
- Check engine light
- Dirty transmission fluid/filter
- Clogged hydraulic passages
- Valve body problems
- Damaged/corroded wiring or connectors
- Failed brake band apply solenoid
How to Diagnose the Code?
The condition of the transmission fluid can often be the cause of a P1851 DTC, as sludge can block passages inside the valve body and affect the operation brake band solenoid. If no issues are show up in the transmission fluid, then it’s a good chance that the brake band solenoid has gone bad.
What Repairs Will Fix P1851?
- Change the transmission fluid and filter (service the transmission)
- Replace or repair damage wiring/connectors
- Replace brake band apply solenoid
P1850 – Brake Band Apply Solenoid Circuit
P1852 – Brake Band Apply Solenoid Low Voltage
P1853 – Brake Band Apply Solenoid High Voltage