Transmission Fluid Pressure Sensor/Switch Circuit Malfunction
The P0870 code indicates a problem in the electrical circuit of the transmission fluid pressure sensor or switch. This sensor monitors hydraulic pressure inside the transmission and sends a signal to the powertrain control module (PCM). When the PCM detects a voltage or resistance reading outside the expected range, it sets this code. Common causes include a faulty sensor, damaged wiring, poor electrical connections, or low transmission fluid level. This issue can lead to improper shift patterns, harsh shifting, or transmission slippage.
01. Most Common Causes
- Faulty transmission fluid pressure sensor
- Damaged or corroded wiring/connectors
- Low or contaminated transmission fluid
- Internal transmission mechanical failure
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record 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 the pressure sensor's resistance and voltage with a multimeter and compare to specs.
Step 5: If sensor and wiring are okay, perform a transmission pressure test to rule out internal issues.
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 it can cause transmission damage. You may experience harsh shifting or slipping, which can worsen over time.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on the cause. A sensor replacement is usually $100-$250, while wiring repairs may be less. If internal transmission damage is found, costs can exceed $1,000.