Damaged, chafed or corroded wiring to the pressure sensor or switch; Loose, corroded or contaminated connector at the sensor, solenoid body or control module; Failing transmission fluid pressure sensor or switch giving intermittent output; Low, degraded or contaminated transmission fluid causing unstable pressure readings; Internal transmission wiring loom or valve body fault, on designs where the sensor is inside the unit; Low system voltage or poor earth affecting sensor reference or signal; Faulty transmission control module.

P0874

Transmission Fluid Pressure Sensor/Switch C Circuit Intermittent.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
8: AreaTransmission
74: FaultThe specific fault in that area

What it means

P0874 is a generic powertrain code meaning the transmission control module has detected an intermittent fault in the circuit of transmission fluid pressure sensor or switch 'C'. The module saw the signal drop out, spike or jump to implausible values from time to time rather than staying permanently faulty. Which part of the transmission 'C' refers to depends on the vehicle manufacturer and transmission model.

Symptoms

Gearbox warning light or malfunction indicator lamp on
Harsh, delayed or flared gear changes that come and go
Transmission stuck in limp mode or a fixed gear at times
Slipping or loss of drive under load
Erratic shifting after hitting bumps or when the engine is hot or cold
Reduced fuel economy

Possible causes

Damaged, chafed or corroded wiring to the pressure sensor or switchlikely
Loose, corroded or contaminated connector at the sensor, solenoid body or control modulelikely
Failing transmission fluid pressure sensor or switch giving intermittent outputlikely
Low, degraded or contaminated transmission fluid causing unstable pressure readingspossible
Internal transmission wiring loom or valve body fault, on designs where the sensor is inside the unitpossible
Low system voltage or poor earth affecting sensor reference or signalpossible
Faulty transmission control modulerare

How to diagnose

Read all stored and pending codes and note freeze frame data, such as temperature, speed and gear, to see when the fault occurs
Check the transmission fluid level and condition using the manufacturer's procedure, as some units are sealed and need specific temperature and tooling
Inspect the wiring and connectors to the sensor or switch for chafing, heat damage, fluid ingress, bent pins and corrosion
Wiggle test the harness and connector with live data on display, watching for signal dropouts or jumps
Check battery condition, charging voltage and the control module power and earth connections
Look up the manufacturer's data for which sensor or switch is 'C' on this model, then test its reference voltage, signal and earth against specification
Compare the live pressure sensor or switch reading with expected values in different gears, if the data is available
Check for related codes and any technical service bulletins for the transmission model

How to fix

Repair or replace damaged wiring and fix any chafed sections of the harness
Clean or replace corroded or loose connectors and terminals, and fix any fluid leakage into them
Replace the pressure sensor or switch if testing shows it is faulty
Correct the fluid level or change degraded fluid with the specified type, and fix any leaks
Repair or replace the internal harness or valve body assembly if the fault is inside the transmission
Repair charging or earth faults, and replace or reprogram the control module only when diagnosis confirms a fault or an outdated calibration is a known cause

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but intermittent pressure faults can cause limp mode, slipping and wear to clutches, so get it checked soon. Avoid heavy loads or towing, and stop if the gearbox slips badly or shifts harshly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.