Transmission Fluid Pressure Sensor/Switch C Circuit High
What does P0873 mean?
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.
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
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Measure voltage at sensor C connector with key on, engine off
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Check for an open ground wire at the sensor
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Test for short to battery voltage on the signal wire
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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.