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.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $500 (parts and labor)
Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.
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
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.
Mechanics Guide Step-by-step diagnosis
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
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Commonly Affected Vehicles
- 2010-2020 Ford Explorer (10R80)
- 2012-2019 GM Tahoe (8L90)
- 2011-2019 Jeep Grand Cherokee (ZF 8HP)
- 2013-2020 Chrysler 300 (ZF 8HP)
Related Codes
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