Transmission Fluid Pressure Sensor/Switch Circuit Low
The P0877 code indicates that the Transmission Control Module (TCM) has detected a low voltage signal from the transmission fluid pressure sensor or switch circuit. This sensor monitors hydraulic pressure inside the transmission to ensure proper shifting and torque converter operation. A low circuit condition can be caused by a faulty sensor, damaged wiring, poor electrical connections, or low transmission fluid level. This issue can lead to erratic shifting, slipping, or transmission damage if not addressed promptly.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Erratic or harsh shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
2. Most Common Causes
- Faulty transmission fluid pressure sensor
- Damaged or corroded wiring/connectors in the sensor circuit
- Low transmission fluid level or contaminated fluid
- Internal transmission mechanical failure
3. Step-by-Step Diagnosis
Step 1: Scan for additional 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 signal voltage with a multimeter; compare to manufacturer specs.
Step 5: If sensor and wiring are OK, perform a transmission pressure test to rule out internal issues.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as low transmission fluid pressure can cause internal damage and lead to costly repairs.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for sensor replacement, but can be higher if wiring repairs or transmission service is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.