P0848
Transmission Fluid Pressure Sensor/Switch B Circuit High
Powertrain Transmission Control Transmission Pressure Sensor 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The transmission fluid pressure sensor is reading too high, like a water pressure gauge stuck on the high end of the dial. This tells the engine computer something is wrong with the sensor circuit or the actual pressure in the transmission.

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Symptoms You May Notice
3 known symptoms for this code
Transmission warning light or check engine light illuminated
Harsh or delayed gear shifts
Transmission may go into limp mode or default gear
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors voltage from the transmission fluid pressure sensor B, expecting a signal that correlates to actual fluid pressure. When the sensor voltage exceeds the maximum threshold, the ECM logs a high circuit fault. This could indicate a shorted sensor, wiring issue, or genuine high pressure condition.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor voltage 0.5–4.5 volts (correlates to pressure range) Above 4.8 volts or circuit impedance too low
Pressure reading 50–350 PSI (depending on gear/load) Signal indicates >380 PSI continuously
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Transmission fluid level
Check and top off transmission fluid to proper level; overfilled fluid causes false high pressure readings.
2
Sensor wiring harness and connector
Inspect the B sensor connector for corrosion, loose pins, or water intrusion; clean or reseat as needed.
3
Transmission fluid pressure sensor B
Replace the sensor if it reads high when fluid level and wiring are confirmed good.