What does it mean?
P1551 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Secondary Or Primary Fuel Level Sensor Malfunction .
Symptoms
- Fuel gauge stuck on empty or full, or jumping erratically while driving
- Low fuel warning lamp on with a full tank, or no warning at all when the tank is nearly empty
- Check engine light on and a distance-to-empty display showing nonsense values
- Gauge needle swinging over bumps or when cornering
- Evaporative emission monitor never completes, so the vehicle can fail an emissions test
- Trip computer consumption figures that do not match reality
Likely causes
- Worn resistive track on the sender card inside the tank, which is the most common cause on higher mileage vehicles
- Corroded or loose connector on top of the fuel tank or at the pump module flange
- Stuck, cracked or fuel-soaked float that no longer follows the fuel level
- Chafed, broken or rodent-damaged wiring running along the underbody to the tank
- Poor sender ground or a high resistance ground point
- On vehicles with a saddle tank, a failed secondary sender while the primary one still reads correctly
- Contaminated or watered fuel that has corroded the sender contacts
How to fix it
- Compare the fuel level value on the scan tool with the actual amount of fuel in the tank
- Inspect the connector at the tank access panel or under the rear seat for corrosion and moisture
- Backprobe the sender signal wire and watch how the voltage changes as fuel is added or drained
- Check continuity and resistance of the sender wiring and its ground back to the module
- On a removed sender, sweep the float by hand and look for dead spots in the resistance reading
- Replace the sender or the complete pump module when the resistance sweep is not smooth
- Clear the code and verify a correct gauge sweep over at least one full tank of fuel