Transmission Fluid Pressure Sensor/Switch Circuit Range/Performance
The P0871 code indicates that the Transmission Control Module (TCM) has detected a signal from the transmission fluid pressure sensor that is outside the expected range or performance parameters. This sensor monitors hydraulic pressure within the transmission to ensure proper shift timing and line pressure. A fault can cause erratic shifting, slipping, or harsh engagement, potentially leading to transmission damage if ignored.
01. Most Common Causes
- Faulty transmission fluid pressure sensor
- Wiring or connector issues (open, short, corrosion)
- Low or contaminated transmission fluid
- Internal transmission mechanical problems
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Erratic or harsh shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors for damage, corrosion, or loose connections.
Step 4: Test sensor resistance and voltage with a multimeter and compare to manufacturer specs.
Step 5: If sensor is faulty, replace it; if wiring is damaged, repair as needed.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the transmission may shift erratically or slip, leading to internal damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for a sensor replacement, plus diagnostic fees. Wiring repairs may add to the cost.