P0874

Code

Generic P — Powertrain

Transmission Fluid Pressure Sensor/Switch C Circuit Intermittent

Brand: Generic

Type: P — Powertrain

Views: UK: 28 EN: 49 RU: 32

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Page language: EN

Causes

Loose, corroded, or damaged sensor connector or terminals
Broken, chafed, or shorted wiring in the sensor harness
High-resistance connection (corrosion, pin push-out)
Faulty transmission fluid pressure sensor/switch C
Intermittent internal failure in the transmission control module (TCM/PCM)
Water intrusion or contamination at connector

Symptoms

MIL (Check Engine/Transmission light) illuminated
Intermittent or erratic shifting (harsh shifts, delayed engagement)
Transmission may go into limp/limitation mode
Unusual transmission noise or hunting between gears
Possible loss of drive or refusal to shift under load

What to check

Retrieve freeze frame and full scan-tool data for stored P0874 and related codes
Visually inspect sensor C connector and harness for damage, corrosion, or contamination
Backprobe the sensor connector and monitor live signal while wiggle-testing the harness
Measure reference voltage (usually 5 V) and ground at the sensor with ignition on
Check sensor signal voltage for stable values or dropouts using a DVOM or preferably an oscilloscope
Perform continuity and resistance checks of the harness between sensor and TCM

Signal parameters

Reference voltage: typically ~5.0 V (key ON) — verify against manufacturer spec
Signal output: varies with pressure; typical range ~0.1–4.9 V (manufacturer specific)
Ground: low resistance to chassis ground
Intermittent code behavior: signal drops to open/OL, sudden spikes, or random noise
If sensor is a switch: open/closed state transitions rather than analog voltage

Diagnostic algorithm

Connect an OBD-II scanner, record freeze-frame and live data. Note whether P0874 is current or historic and any other transmission-related codes.
Visually inspect the transmission fluid pressure sensor C connector and wiring for damage, corrosion, loose pins, insulation abrasion, or water entry.
With ignition ON (engine off), backprobe the sensor connector: verify reference voltage (≈5 V), sensor ground continuity, and observe signal voltage for presence and stability.
Start the engine and monitor live sensor data while performing a wiggle test on the wiring harness and connector to try to reproduce the intermittent. Watch for sudden voltage drops or noise.
If intermittent behavior is observed, use an oscilloscope to capture signal waveform while manipulating the harness to locate intermittent open or short conditions.
Perform continuity and resistance checks between the sensor pins and the TCM connector; repair any high-resistance or open faults found.
If wiring and connectors test good, replace the transmission fluid pressure sensor/switch C with a known-good unit, then clear codes.
After repairs, reset the code, perform a full road test and re-scan. Confirm code does not return and transmission behavior is normal. If code returns and wiring/sensor are good, consider TCM diagnostics or reprogramming.

Likely causes

Worn or corroded connector pins at the pressure sensor
Wire insulation rubbed through and intermittently contacting ground or power
Sensor internal intermittent failure due to heat or contamination
Poor ground or reference voltage caused by connector contamination
Intermittent TCM input circuit or software anomaly (less common)

Fault status

⚠️ Status

Transmission Fluid Pressure Sensor/Switch C Circuit Intermittent — unstable or intermittent electrical signal detected on pressure sensor/switch C circuit (open, short, or noise).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours