P0845
Transmission Fluid Pressure Sensor/Switch B Circuit
Transmission controls
Generic OBD-II
Medium
What it means
P0845 indicates a fault in the circuit for the transmission's "B" fluid-pressure sensor/switch, so the controller can't trust its pressure reading. The engine starts and runs fine, but shift quality can suffer — delayed, harsh, or slipping shifts — and the transmission may drop into a protective limp mode. Check fluid level first, then the sensor and its wiring.
Medium
Can I keep driving? Usually drivable, but if the transmission slips or shifts harshly, drive gently and get it checked to avoid internal damage.
Common symptoms
What you'll notice
- Check-engine light on
- Delayed or harsh shifting
- Transmission slipping
- Difficulty shifting into or out of gear
- Transmission may enter a fail-safe (limp) mode
Common causes
Most likely first
- Low or dirty transmission fluidLikely
- Faulty transmission fluid pressure sensor/switch 'B'Common
- Damaged wiring or a short/open in the sensor circuitCommon
- Loose or corroded connector at the sensorLess often
- Failed transmission control module (rare)Less often
How to diagnose & fix
Work through it in order
- Check transmission fluid level and condition before anything else.
- Read freeze-frame data and inspect the sensor 'B' connector and wiring for corrosion or damage.
- Measure the sensor's signal and reference voltages against spec; back-probe the connector.
- Replace the fluid pressure sensor/switch if it reads out of range.
- Repair any wiring faults, then clear the code and road-test through the gears.
FAQ
Quick answers
Is it safe to drive with P0845?+
Brief driving is usually okay, but slipping or harsh shifts can overheat and damage the transmission. Check fluid and get it diagnosed promptly.
Can I just clear P0845?+
It will return until the sensor or wiring is repaired. Confirm the fluid level first — low fluid alone can trigger this.
Related codes
Often seen with P0845
Read & clear P0845 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX