What does it mean?
P1477 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: EVAP Emission Control LDP Circuit Malfunction .
Symptoms
- MIL on
- EVAP monitor never sets to ready
- No pump operation heard during the leak test
- The vehicle usually drives with no noticeable change
- Fuel vapour smell around the rear of the vehicle in some cases
Likely causes
- Electrical fault in the pump control or signal circuit, such as an open, a short or high resistance
- Failed leak detection pump assembly
- Connector under the vehicle corroded by water and road salt
- Damaged harness section near the fuel tank or charcoal canister
- Loss of power feed or a poor ground for the pump
- Restricted or disconnected vent hose preventing normal pump operation
- Module driver fault
How to fix it
- Check for companion EVAP codes to narrow the fault to the control side, the signal side or flow
- Inspect the pump connector and its harness for corrosion and physical damage
- Verify power and ground at the pump with the key on
- Measure solenoid coil resistance against specification
- Command the pump on and confirm it runs and produces a pressure change
- Inspect the hoses and the canister filter for restriction
- Repair wiring or replace the pump, then verify with a complete EVAP monitor run