What it means
The transmission fluid pressure sensor/switch C reports a circuit intermittent fault. Hydraulic pressure feedback for shift control is unreliable on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Transmission pressure sensor/switch C reports hydraulic pressure feedback to the control module. P0874 sets when the C-circuit signal cuts in and out instead of remaining dependable, often because a loose connector or chafed wire loses contact as the vehicle moves or vibrates.
Common causes
Most likely first.
- Connector not seated
- Harness chafing intermittently
- Connector with intermittent contact under vibration
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and review stored or pending faults alongside live sensor C data to see when the signal drops out.
- Inspect sensor C's connector for incomplete seating, loose pins, corrosion, or fluid contamination.
- Follow the C-circuit harness and look for chafing, stretched sections, or damage near moving parts and hot surfaces.
- With live data displayed, gently move accessible sections of the C-circuit harness and connector to see whether the reading or fault changes.
- If the fault persists, test the C signal, reference, and ground circuits for intermittent opens or resistance changes using the manufacturer's procedure.
Common fixes
- Fully seat and secure the sensor C connector.
- Clean corroded terminals or repair loose connector pins.
- Repair or replace chafed wiring in the C circuit.
- Replace pressure sensor/switch C if it intermittently loses output after wiring and connector faults are ruled out.
Can I keep driving?
Keep trips short and avoid towing or demanding driving while the signal is dropping out, particularly if shifts become harsh or the vehicle enters limp mode. An intermittent loss of C feedback can cause unpredictable shifting and allow slipping to damage the transmission.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.