P0870 Fault Code

Transmission Fluid Pressure Sensor/Switch C Circuit

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0870 fault code indicates a problem with the Transmission Fluid Pressure Sensor/Switch C Circuit, which monitors and reports the hydraulic pressure within the transmission system. This information is crucial for the transmission control module (TCM) to make accurate adjustments for optimal vehicle performance.

• Sensor Overview: The transmission fluid pressure sensor provides real-time pressure data to the vehicle's computer system. When this sensor or its circuit malfunctions, it may lead to erratic shifting, poor fuel economy, or even transmission failure in severe cases.
• Importance of Fluid Pressure: Maintaining correct fluid pressure is vital for the smooth operation of the transmission. If the pressure is too low or too high, it can lead to a range of transmission issues, making the P0870 code significant in diagnosing potential problems.

What are the symptoms of the P0870 code?

Drivers experiencing a P0870 code may notice several symptoms, such as:

• Erratic Shifting: The transmission may hesitate or shift roughly between gears.
• Warning Lights: Check engine light or transmission warning indicators may illuminate on the dashboard.
• Poor Acceleration: There may be a noticeable decrease in acceleration performance.
• Transmission Slipping: Gears might slip unexpectedly, creating a potential safety hazard.
• Fluid Leaks: Signs of transmission fluid leakage may also accompany this code.

What causes the P0870 code?

There are several factors that can lead to a P0870 code:

• Faulty Transmission Fluid Pressure Sensor: The sensor itself may be defective or have failed entirely.
• Wiring Issues: Damaged or corroded wiring in the circuit can disrupt the signal sent from the sensor to the TCM.
• Faulty TCM: In some cases, the issue may lie within the transmission control module, which may not be processing the sensor's signals correctly.
• Low Transmission Fluid: Inadequate fluid levels can also cause pressure issues which would trigger this code.

How to fix P0870?

To resolve a P0870 fault code, the following steps should be taken:

• Diagnostic Scan: Use an OBD-II scanner to confirm the fault code and rule out other related codes.
• Inspect Wiring and Connectors: Check for damaged wiring, loose connections, or corrosion in the sensor circuit.
• Test the Sensor: Assess the transmission fluid pressure sensor for proper operation and replace it if faulty.
• Check & Replenish Fluid: Ensure the transmission fluid is at the correct level and in good condition; top off or replace if necessary.
• TCM Evaluation: If no issues are found with the sensor or wiring, have the transmission control module evaluated or reprogrammed.