P0873 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch C Circuit High

P0873 code definition

The P0873 trouble code refers to a detected anomaly in the transmission fluid pressure. The reported pressure has fallen beyond the manufacturer's set parameters.

What the P0873 code means

The vehicle's Powertrain Control Module (PCM) is fed information on many aspects of the vehicle's systems, including transmission fluid pressure. In a P0873, the sensor in the transmission system's C circuit has detected a pressure level that extends beyond the manufacturer's set limits.

What causes the P0873 code?

A P0873 is most often caused by a problematic transmission system.

• Dirty, contaminated or burnt transmission fluid is the most common cause
• Mechanical problems with the transmission system
• A faulty or damaged transmission system
• Faulty sensor or overheated engine

In very rare cases, the PCM itself may be faulty and reporting false information. Because PCMs are notoriously difficult to repair or reprogram, this slight possibility should only be considered if all other possible causes have been exhausted completely.

What are the symptoms of the P0873 code?

A P0873 scenario typically involves problems with the transmission. When the vehicle is being used, there will usually be a distinct smell of burnt transmission fluid, as well as smoke possibly emanating from the transmission system. Practical concerns regarding the transmission system, including gear slippage, are also possible. For the sake of identifying and diagnosing the issue, the P0873 code and dashboard trouble lamp will be activated to alert the operator.

How does a mechanic diagnose the P0873 code?

The P0873 trouble code may be first diagnosed by uplinking to the vehicle's onboard computer with an OBD-II code reader. The components related to the transmission system (including the sensor that picked up the issue) should be thoroughly inspected for signs of wear. If a leak has been detected at some part of the transmission system's body, a visual mark of it should be made for reference during the repair stage.

Common mistakes when diagnosing the P0873 code

Technicians have reported the P0873 code cause to be underestimated and mistakenly blamed on bad transmission fluid. Instead, the primary cause (a faulty transmission pump, for instance) may have subsequently resulted in fluid issues.

How serious is the P0873 code?

A P0873 trouble code suggests there are serious issues with the transmission system. Because of this, it is not recommended using the car until the transmission system has been checked thoroughly and addressed accordingly.

What repairs can fix the P0873 code?

• If any components in the transmission system (including the sensor itself) have been identified as faulty, they should be repaired or replaced outright

• Leaky segments in the transmission system should be patched up and repaired

• Any corroded, broken or faulty wiring related to the transmission system, including connectors, should be repaired accordingly

• Following your set of repairs, the vehicle should be test-driven immediately. Giving the vehicle a few minutes of use will allow you to see whether or not the code has been solved

• In the rare instance that the PCM itself may be faulty, it will need to be repaired and reprogrammed, or replaced outright

Due to the expensive and long time it takes to commit to PCM repairs, this option should only be pursued if it's made absolutely clear that the PCM is at fault.

Additional comments for consideration regarding the P0873 code

The particular pressure limits needed to trigger a P0873 code will vary depending on the model and manufacturer of the vehicle.

Need help with a P0873 code?

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