What does it mean?
P1478 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: EVAP Emission Control LDP Circuit Clamped Tube Detected .
Symptoms
- MIL on
- EVAP monitor fails or never completes
- Slow fuel filling, with the nozzle clicking off repeatedly if the vent path is fully blocked
- No pumping action from the leak detection pump
- Engine performance is normally unaffected
Likely causes
- Pinched, kinked or crushed EVAP hose between the pump, the canister and the tank
- Canister filter packed with dirt, mud or insect nests
- Water frozen in the vent line in cold weather
- Aged rubber hose that has collapsed shut under vacuum
- Hose incorrectly routed or over-clamped after tank or suspension work
- Vent valve stuck closed and holding the line shut
- Pump internal valving failing and reporting a false blockage
How to fix it
- Trace the EVAP lines from the pump to the canister and tank looking for kinks and crushed sections
- Remove and inspect the canister filter for dirt and insect nests
- Blow low pressure air through each line to confirm free flow
- Command the vent valve with a scan tool and confirm it opens
- Straighten or replace collapsed hoses and secure them clear of moving parts
- Retest the pump once the restriction has been cleared
- Clear the code and rerun the EVAP monitor to verify