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DTC codes / P08xx · Transmission / P0874

P0874Transmission Fluid Pressure Sensor/Switch 'C' Circuit Intermittent

P0874 means the transmission control module (TCM) has detected an intermittent fault in the electrical circuit for transmission fluid pressure sensor or switch 'C'. The TCM sees the signal from this sensor drop out or become erratic for brief periods, rather than failing completely, so the code is stored when the circuit does not behave consistently.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other symptoms
  • Harsh or delayed gear shifts, especially when the transmission is cold
  • The transmission may slip or fail to engage a gear momentarily
  • Intermittent limp mode or reduced power, resetting after the ignition is cycled
  • Erratic shift quality that comes and goes without a clear pattern

Common causes, most likely first

  1. A faulty transmission fluid pressure sensor or switch 'C' that fails intermittently when hot or under vibration
  2. Damaged, chafed, or corroded wiring in the sensor 'C' circuit, often near connectors or where the harness bends
  3. Loose or contaminated electrical connector at the sensor or at the transmission case pass-through
  4. Low or degraded transmission fluid causing pressure fluctuations that confuse the sensor signal
  5. Internal transmission wear or a sticking valve body that produces erratic pressure readings
  6. A failing transmission control module (TCM) or poor ground connection for the sensor circuit

How to diagnose and fix it

  1. Check the transmission fluid level and condition first, topping up or servicing if the fluid is low or burnt
  2. Inspect the sensor 'C' connector and wiring for corrosion, loose pins, or chafed insulation, repairing as needed
  3. Clear the code and test-drive while monitoring live pressure sensor data to see if the signal drops out intermittently
  4. Perform a resistance and voltage drop test on the sensor 'C' circuit from the TCM connector to isolate a bad wire or sensor
  5. Replace the transmission fluid pressure sensor or switch 'C' if the circuit tests good but the signal remains erratic
  6. Check and clean the TCM ground connections and inspect the TCM connector for signs of water intrusion
  7. If the fault persists after electrical repairs, perform a transmission pressure test to rule out internal hydraulic problems

Why an intermittent pressure code misleads

  • An intermittent code like P0874 often sets because of a momentary wiring glitch, not a failed sensor, so replacing the sensor first can be a costly guess.
  • The sensor 'C' circuit may share a ground or reference voltage with other sensors, so a fault elsewhere on that shared circuit can trigger this code.
  • Heat and vibration frequently cause the circuit to act up only when the transmission is at operating temperature, making the fault hard to reproduce cold.
  • A low fluid level or a clogged transmission filter can create pressure pulsations that the sensor reports as intermittent, mimicking an electrical fault.
  • Some vehicles store P0874 as a pending code without turning on the warning light, so it may be found during a scan for an unrelated issue.

Can I keep driving with P0874?

You can usually drive short distances at moderate speed, but avoid heavy towing or aggressive acceleration until the fault is repaired. If the transmission begins slipping, shifting harshly, or entering limp mode, stop driving and have it diagnosed to prevent internal damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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