What Does P0871 Mean?
The TCM has determined that the transmission fluid pressure sensor/switch 'C' circuit output is not within the expected range for the current operating conditions, or the signal is not performing as expected during shifts. This range/performance code indicates the sensor is providing a signal but it doesn't correlate logically with commanded pressure or gear state.
Common Causes
30%
Degraded or contaminated transmission fluid affecting pressure response
25%
Transmission fluid pressure sensor 'C' drifting out of calibration
20%
Internal valve body wear affecting pressure regulation in circuit 'C'
15%
Intermittent wiring issue causing erratic sensor signal
10%
Worn clutch pack or accumulator in circuit 'C'
Diagnostic Steps
1
Check transmission fluid condition and level — degraded fluid can cause abnormal pressure behavior.
2
Monitor live pressure data from sensor 'C' during a road test, noting how pressure changes with shift commands and throttle position.
3
Compare sensor 'C' readings to a mechanical gauge test at the appropriate test port to verify sensor accuracy.
4
Inspect the wiring harness for intermittent breaks by wiggling connectors while monitoring live data.
5
If sensor and wiring check out, a valve body inspection may be required to check for worn bores or stuck valves.
Estimated Repair Cost
$150 - $1,000
Parts + labor, varies by vehicle and location
The TCM has determined that the transmission fluid pressure sensor/switch 'C' circuit output is not within the expected range for the current operating conditions, or the signal is not performing as expected during shifts. This range/performance code indicates the sensor is providing a signal but it...
The most common cause of P0871 (Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance) is: Degraded or contaminated transmission fluid affecting pressure response
Typical repair costs for P0871 range from $150 to $1,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive with awareness. Shift quality may be compromised with potential for slipping or flare-ups during shifts. Avoid towing and aggressive acceleration until diagnosed.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0871 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Transmission Hydraulic Pressure Monitoring
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
