P1459
EVAP Purge Flow Switch Malfunction.
- Honda
- Powertrain
- Manufacturer code
- Low severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 4
- AreaAuxiliary emission controls
- 59
- FaultThe specific fault in that area
What it means
On Honda vehicles P1459 means the engine control unit has found a fault with the EVAP purge flow switch circuit or its reported state. The switch (or a pressure-type sensor doing the same job on some models) should change state when the purge control valve opens and closes, and the control unit saw a signal that did not match the commanded purge. The exact hardware varies by model and year, so confirm against the correct service information.
Symptoms
- Malfunction indicator lamp on
- Possible failed emissions test or readiness monitor not completing
- Fuel smell around the fuel tank or engine bay in some cases
- Difficulty refuelling, with the pump clicking off repeatedly
- Usually no noticeable change in driveability
Possible causes
- Faulty or stuck EVAP purge control valve (solenoid) giving the wrong flowlikely
- Faulty purge flow switch or sensor, or a failed internal signallikely
- Damaged, chafed or disconnected wiring or a corroded connector at the switch or purge valvepossible
- Blocked, kinked, cracked or disconnected EVAP vacuum hoses or pipespossible
- Saturated or blocked charcoal canister, often after tank overfillingpossible
- Fault in the engine control unitrare
How to diagnose
- Read the stored and pending codes and note the freeze frame data, including engine temperature and fuel level, and check for other EVAP codes.
- Visually inspect the purge flow switch, the purge valve and their connectors for damage, corrosion, loose pins or water ingress.
- Inspect all EVAP hoses and pipes between the canister, purge valve and intake for splits, kinks, loose joints and fuel contamination.
- Check the purge valve resistance and its operation against the manufacturer's specification, and listen for it clicking when commanded.
- Check the purge valve for sticking open or closed by testing for vacuum holding and flow with the valve unpowered and commanded.
- With a scan tool, view the switch state while commanding purge, and compare it with the expected values for the model.
- Check the supply, earth and signal wiring from the switch to the control unit for continuity, short circuits and voltage.
- Inspect the charcoal canister for liquid fuel or blockage, and check the fuel cap seal.
How to fix
- Replace the purge control valve if it sticks or fails the electrical or flow tests.
- Replace the purge flow switch or sensor if it fails to change state correctly.
- Repair or replace damaged wiring and connectors, and clean the terminals.
- Replace cracked, blocked or disconnected EVAP hoses and fittings.
- Replace the charcoal canister if it is saturated with fuel or blocked, and address the cause such as overfilling.
- After repair, clear the code and complete a drive cycle to confirm the EVAP monitor runs and passes.
Can I keep driving?
The car can normally be driven as the fault mainly affects the evaporative emissions system. Book it in soon, as it will keep the warning lamp on and may fail an emissions test, and fuel vapour leaks should not be ignored.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.