P1871
Undefined Gear Ratio
Severity
🔴 HighCan you drive?
Do not drive — repair immediately
Approx. repair cost
$56–278 (est.)
Symptoms
- Erratic gear shifting
- Dips during acceleration
- Switching to emergency mode of automatic transmission operation
- Increased fuel consumption
- Check Engine Light Illuminates
Causes
- Low transmission fluid level
- Friction disc wear
- Malfunction of input/output shaft speed sensors
- Problems with the hydraulic block
- Transmission fluid contamination or degradation
How to Fix
- Check the level and condition of the transmission fluid
- Diagnose speed sensors and their circuits
- Check the hydraulic pressure in the system
- Perform computer diagnostics of automatic transmission
- If necessary, replace worn friction discs