The transmission brake band is used to stop a spinning drum inside the transmission to allow for a gear change. Having a P1850 diagnostic trouble code means there is an issue with the brake band apply solenoid, which is used to direct the flow of pressurized hydraulic fluid/ATF that activates the transmission band.
How Serious is the Code?
A P1850 OBDII diagnostic trouble code is a very serious DTC, because it means the ECU/TCM is not in full control of the brake band. This is one of the most important transmission parts, as it facilitates a gear change. Problems with this can result in serious drivability issues.
Symptoms of a P1850 include:
- Delayed gear changes
- Erratic transmission behavior
- Burning smell coming from the transmission
- Transmission overheating
- Check engine light
- Dirty transmission fluid
- Blocked hydraulic passages
- Valve body issues
- Damaged/corroded wiring or connectors
- Failed brake band apply solenoid
How to Diagnose the Code?
With diagnosing a P1850 DTC, it’s important to pay attention to the condition of the transmission fluid, as this can have a huge effect on the operation of the brake band solenoid. If the transmission fluid is in good condition, then the valve body and brake band solenoid should be investigated as a possible culprit for the problem.
What Repairs Will Fix P1850?
- Change the transmission fluid and filter
- Replace or repair damage wiring/connectors
- Replace brake band apply solenoid
P1851 – Brake Band Apply Solenoid Performance
P1852 – Brake Band Apply Solenoid Low Voltage
P1853 – Brake Band Apply Solenoid High Voltage