P0873 moderate

Transmission Fluid Pressure Sensor/Switch C Circuit High

The P0873 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch C Circuit High. This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $100 - $500 (parts and labor)

Check Your Fluid First

ANCEL AD310 OBD-II Scanner

Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.

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Read Transmission Codes

LAUNCH CRP123X (Reads All Systems)

Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.

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Common Symptoms

Check Engine Light illuminated
Harsh shifts in certain gears
Transmission may not upshift smoothly
Possible limp mode

Probable Causes (Ranked by Likelihood)

Open ground wire at pressure sensor C Very High
Faulty pressure sensor C reading high High
Short to voltage in sensor C signal wire Moderate
TCM reference voltage issue for sensor C Low

Step-by-Step Diagnostic Procedure

Measure voltage at sensor C connector with key on, engine off
Check for an open ground wire at the sensor
Test for short to battery voltage on the signal wire
Replace sensor C if wiring checks are normal

Frequently Asked Questions

What happens if the TCM thinks pressure is higher than it is?

The TCM may reduce solenoid output to lower pressure, but since the actual pressure is already normal or low, this can cause insufficient clamping force and clutch slippage.

Can I test sensor C with a multimeter?

Yes, you can check the sensor resistance and the voltage at the connector. Compare your readings to the manufacturer specifications in the service manual.

Are 8-speed and 10-speed transmissions more prone to pressure sensor issues?

They have more sensors and more complex hydraulic circuits than older transmissions, which means more potential points of failure. However, they are generally reliable when properly maintained.