P0845
UniversalTransmission Fluid Pressure Sensor/Switch B Circuit
Medium SeverityThis code indicates a problem with the electrical circuit for the Transmission Fluid Pressure Sensor/Switch B, which monitors the hydraulic pressure within the transmission. A fault here can lead to incorrect gear shifts, transmission slipping, or the transmission entering a 'limp mode' to prevent further damage.
⚠️ Before You Begin (Safety First)
Always wear appropriate personal protective equipment, such as gloves and eye protection, when working on your vehicle. Ensure the vehicle is parked on a level surface with the parking brake engaged and the engine off before attempting any repairs. Disconnect the battery before working on electrical components to prevent accidental shorts or injury.
Common Symptoms
- Check Engine Light illuminated
- Transmission slipping
- Hard shifting or erratic gear changes
- Delayed engagement of gears
- Transmission entering 'limp mode'
- Poor fuel economy
Common Causes
- Faulty Transmission Fluid Pressure Sensor/Switch B
- Damaged or corroded wiring or connectors in the sensor circuit
- Short circuit or open circuit in the sensor wiring
- PCM (Powertrain Control Module) fault (less common)
Frequently reported on: General/Universal
Diagnostic Steps
- Visually inspect the wiring and connectors leading to the Transmission Fluid Pressure Sensor/Switch B for damage, corrosion, or loose connections.
- Check the transmission fluid level and condition; ensure it's at the correct level and not burnt or excessively dirty.
- If accessible, use a multimeter to test the resistance and voltage of the sensor circuit according to vehicle-specific repair manual specifications.
- If the sensor is found to be faulty, replace the Transmission Fluid Pressure Sensor/Switch B.
- Clear the P0845 code using an OBD-II scanner and test drive the vehicle to confirm the repair.
👨🔧 When to Call a Professional
If you experience severe transmission symptoms like hard shifting, slipping, or a complete loss of gear engagement, it's best to consult a professional mechanic immediately to prevent further damage to the transmission.
Commonly Asked Questions
Can I drive with a P0845 code?
It's generally not recommended to drive for an extended period with this code, as it can lead to further transmission damage or unsafe driving conditions if the transmission shifts unexpectedly or enters limp mode.
Where is the Transmission Fluid Pressure Sensor/Switch B located?
Its exact location varies by vehicle, but it's typically found within or mounted on the outside of the transmission housing, often on the valve body.
Is this sensor difficult to replace?
The difficulty depends greatly on its location and accessibility. Some sensors are external and relatively easy to reach, while others may require dropping the transmission pan or even removing the transmission.
What is 'limp mode'?
Limp mode is a protective feature where the vehicle's computer limits transmission functions (e.g., locking it into a single gear) to prevent severe damage when a serious fault is detected.
Will changing the transmission fluid fix this code?
While low or dirty fluid can cause transmission problems, a P0845 code specifically points to a circuit issue with the sensor. Changing fluid alone is unlikely to fix a sensor or wiring fault, but it's good practice to ensure fluid is correct.