P0845
Transmission Fluid Pressure Sensor/Switch B Circuit
Powertrain Transmission Control Pressure Sensor Circuit 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The transmission fluid pressure sensor isn't sending the right signal to your engine computer, like a broken gauge on your dashboard. This prevents the transmission from shifting properly because the ECU can't tell how much pressure is in the fluid.

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Symptoms You May Notice
3 known symptoms for this code
Transmission stuck in one gear or limp mode
Check Engine Light illuminated
Harsh or delayed gear shifts
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the voltage signal from the transmission fluid pressure sensor to verify actual fluid pressure levels. It compares this signal against expected pressure thresholds for each gear and driving condition. If the voltage is out of range or missing, a fault is triggered.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor Voltage 0.5V - 4.5V (proportional to pressure) Below 0.1V or above 4.9V, or no signal detected
Fluid Pressure 20-350 PSI depending on gear Pressure reading inconsistent with gear selection
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Transmission wiring harness connector
Inspect and reseat the sensor connector for corrosion or loose pins.
2
Transmission fluid
Check fluid level and condition; low or contaminated fluid causes sensor reading errors.
3
Transmission fluid pressure sensor
Replace the sensor if wiring and fluid are good; it may be internally failed.