P0497 EVAP system low purge flow

EVAP low purge flow

Monitor

EVAP faults let fuel vapour escape but rarely change how the car drives, and the main risk is a failed emissions test, so it is safe to drive while you arrange a fix.

It gets more serious if:

  • Inspect soon: You keep smelling raw fuel around the car, not just right after filling up
  • Stop: You see liquid fuel dripping or pooling under the car, or near the filler, tank or canister

Source: how we rate severity

P0497 in short

P0497 means the computer saw too little fuel vapour flowing from the charcoal canister into the engine when it opened the purge valve. Common causes are a purge valve that does not open, blocked purge lines, or a canister soaked with fuel from overfilling. It is safe to drive.

Fuel vapour is stored in a charcoal canister and drawn into the engine through the purge valve. The computer must check that this purge flow actually happens, and it sets P0497 when the flow is too low.

A purge valve that stays shut, a blocked or kinked line, or a canister and lines soaked with liquid fuel can all cut the flow. GM's bulletin for the Volt replaces any EVAP part soaked with fuel and warns that overfilling the tank brings the problem back.

P0496 is the opposite fault (flow when there should be none), so check which one you have before buying a purge valve.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Purge valve that does not open when commanded

    Common general cause
    Why it ranks here
    The purge valve controls the flow being measured, and a valve that stays shut stops it completely.
    What would change this
    Rises if the valve does not open or click when a shop commands it. Falls if vacuum reaches the canister side when it is open.
    How to test the evap canister purge valve

  2. Canister or EVAP parts soaked with liquid fuel

    Possible — needs testing
    Why it ranks here
    GM replaces EVAP parts soaked with liquid fuel for P0497, and Nissan explains that topping off the tank can flood the canister.
    What would change this
    Rises if the tank is often filled past the first click, or the canister or lines contain liquid fuel.
    How to test the evap charcoal canister

  3. Blocked or kinked purge line

    Possible — needs testing
    Why it ranks here
    GM has technicians blow out the EVAP lines, because a restricted line cuts purge flow.
    What would change this
    Rises if a line is kinked, crushed or holds fuel.
    How to test the vacuum hoses and intake leaks

  4. Disconnected or leaking purge-side hose

    Possible — needs testing
    Why it ranks here
    Honda's bulletin title pairs low purge flow with an internal vacuum leak, and a hose that is off its fitting can rob the flow.
    What would change this
    Rises if a purge hose is off, split or loose.
    How to test the vacuum hoses and intake leaks

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored and pending codes and note any other purge codes.

    Low riskTool: OBD-II scan tool

  2. Think about how the tank is filled. Do you keep filling after the pump clicks off?

    Low risk

  3. With the engine off and cool, look at the purge valve hoses you can reach.

    Use cautionTool: flashlight

    Warning:Fuel vapour is flammable. Work outdoors with the engine off and cool, and keep sparks, cigarettes and open flames away.

  4. Have a shop command the purge valve open with a scan tool and check for vacuum and flow through it and the lines.

    Best left to a shopTool: scan tool with output controls, vacuum gauge

    Warning:Shop test on the fuel vapour system.

Symptoms

  • Check engine light on, usually with no change in how the car drives
  • Fails an emissions or smog test because of the light or an incomplete EVAP monitor
  • Persistent raw fuel smell around the car Gets more serious: stop and have it checked.
  • Liquid fuel dripping under the car Gets more serious: stop and have it checked.

Compare with: Check engine light came on after getting gas

How to fix

  1. Stop filling once the pump clicks off the first time. Topping off can flood the canister.

  2. After a repair, drive normally for several days so the monitor can re-run. Clearing codes or disconnecting the battery resets readiness, so do it shortly before an inspection only if you then complete a drive cycle.

Parts and cost context

  • EVAP canister purge valve:Confirm it does not open when commanded before replacing it.
  • EVAP charcoal canister:Replace only if it is soaked with liquid fuel. Labour varies, so get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 2011–2015 · Volt

    Supported by vehicle data

    GM PIP4891H covers P0497 on the Volt and the 2014–2016 Cadillac ELR: inspect the EVAP parts, replace any soaked with liquid fuel and blow out the lines. GM warns that overfilling the tank can bring it back. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • PIP4891HStatus unverified

    Service Engine Soon light with P0497, EVAP components saturated with liquid fuel

    2011–2015volt · issued · NHTSA 10160649

    Inspect every EVAP component, replace any that are soaked with liquid fuel and blow out the EVAP lines. Overfilling the tank can make it happen again. The Cadillac ELR (2014–2016) is also covered. Only the NHTSA flat-file summary was reviewed, not the bulletin itself.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Honda

  • 2001–2005 · Civic

    Supported by vehicle data

    Honda bulletin 1105 covers P0497 (low purge flow or internal vacuum leak) on the 2001–2005 Civic. Only its title was reviewed. The bulletin is on NHTSA, but whether it is still current is not verified, so it is labelled vehicle data rather than confirmed.

  • 1105Status unverified

    P0497, low purge flow or internal vacuum leak

    2001–2005civic · issued · NHTSA 10018251

    Covers P0497 on the 2001–2005 Civic. The NHTSA flat file gives only the title, so the repair it prescribes is not described here.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0441EVAP purge flow incorrect

    Same system Common general cause

    Both come from the purge flow check. P0441 is a general incorrect-flow code, P0497 specifically too little flow.

  • P0496EVAP purge flow when purge should be off

    Same system Common general cause

    The opposite fault on the same purge valve: P0496 is flow when there should be none, P0497 too little flow when it should be open.

  • P0443EVAP purge valve circuit fault

    Same system Common general cause

    P0443 is the purge valve circuit code. If it is stored with P0497, start at the purge valve and its circuit.

All EVAP (evaporative emissions) codes

P0497 questions

Can overfilling the tank cause P0497?

It can. GM warns that overfilling can bring P0497 back on some cars, because liquid fuel can soak the canister and lines. Stop when the pump clicks off the first time.

Is P0497 the same as P0496?

No. P0497 is too little purge flow and P0496 is flow when the valve should be shut. Both involve the purge valve, but the causes differ.

Is it safe to keep driving?

Usually yes, as long as there is no strong fuel smell and no fuel dripping. Most makers advise getting it fixed when it is convenient. A strong fuel smell means get it checked soon, and dripping fuel means stop and do not drive.

Will this code fail an emissions inspection?

In states that test OBD-II, a check engine light that stays on with the engine running fails the test. Clearing the code does not help straight away, because the EVAP monitor then reads not ready until the car completes a drive cycle.

Sources and review

  1. Frequently Asked Questions on On-Board Diagnostics (EPA 420-F-97-003) — US EPA ,
  2. On-Board Diagnostic II (OBD II) Systems Fact Sheet — California Air Resources Board ,
  3. EVAP: The Phantom Emissions Menace (Nissan TechNews, May 2018) — Nissan North America (hosted by AutomotiveTechInfo) ,
  4. OBD Test Reference (rev 8.6) — California Bureau of Automotive Repair ,
  5. What do you mean my car is not ready? — New York State DMV
  6. Recall acknowledgement 17V-088: BMW i3 REx fuel tank vent line may chafe — BMW of North America / NHTSA
  7. Part 573 Safety Recall Report 15V-621 (Mazda 8615J): liquid fuel can enter the EVAP canister — Mazda North American Operations / NHTSA
  8. Cal. Code Regs. Tit. 13, § 1968.2 — Malfunction and Diagnostic System Requirements (OBD II) — California Air Resources Board (via Cornell LII)
  9. GM PIP4891H: MIL with P0497, inspect EVAP components for liquid fuel saturation — General Motors / NHTSA ,
  10. Honda 1105: P0497, low purge flow or internal vacuum leak — American Honda / NHTSA ,
  11. Land Rover SSM 74799: P0496 logged — Jaguar Land Rover North America / NHTSA ,
Last reviewed
Written by
Saurabh K.
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