P0456: EVAP System Leak Detected (very small leak)
What Does P0456 Mean?
P0456 is a diagnostic trouble code indicating: EVAP System Leak Detected (very small leak). This code relates to the emission controls system. It has been reported in NHTSA complaints across 35 different vehicle models.
The emission control system reduces harmful exhaust pollutants through several subsystems: EGR (Exhaust Gas Recirculation) recirculates a portion of exhaust back into the intake to lower combustion temperatures and reduce NOx. The secondary air injection system pumps fresh air into the exhaust during cold starts to help the catalytic converter light off faster. The catalytic converter converts CO, HC, and NOx into CO2, H2O, and N2. The EVAP system captures fuel vapors from the tank and purges them into the engine for combustion. When any of these systems malfunction, the vehicle will fail emissions testing and the ECM will set a DTC.
Symptoms of P0456
- ⚠️ Check engine light on
- ⚠️ Failed emissions/smog test
- ⚠️ Possible rough idle or stalling (EGR stuck open)
- ⚠️ Fuel smell (EVAP leak)
- ⚠️ Reduced performance in some cases
- ⚠️ Increased tailpipe emissions
Common Causes
- 🔍 Carbon buildup causing EGR valve to stick
- 🔍 EVAP system leak (gas cap, hose, canister, purge valve)
- 🔍 Catalytic converter below efficiency threshold (aging)
- 🔍 Secondary air pump failure or check valve stuck
- 🔍 Wiring or vacuum line issue in emission control circuit
P0456 Reports by Year
Real Owner Reports
From NHTSA complaint database — actual owner descriptions.
"2005 TOYOTA COROLLA. 3/1/2010-ENGINE CUTS OUT/STALLS WHILE DRIVING AND CHECK ENGINE LIGHT. RETRIEVED CODES P0606 AND P0456. BROUGHT TO LOCAL SERVICE AND WAS DIAGNOSED AS ECM FAILURE. SERVICE REP STATES THAT IT HAS TO GO TO TOYOTA BECAUSE ECM IS ON TECHNICAL SERVICE BULLETIN EXTENDED WARRANTY. "
— Toyota Corolla owner, 03/01/2010
"THE VEHICLE CHECK ENGINE LIGHT COMES ON. THE CODES IDENTIFY IT AS P0456. WHEN WE TOOK IT TO THE DEALER, THEY TRIED TO TELL US THAT AN ANIMAL HAD MADE A SMALL PINHOLE IN THE GAS RETURN LINE. THEY WANTED TO CHARGE 600.00 TO REPLACE THE TANK OR THEY COULD TEMPORARILY FIX IT UNTIL WE COULD GET THAT D"
— Toyota Corolla owner, 10/20/2009
"Recurring Problems with AWD Malfunction, Engine Light On. Contacted Toyota two month ago, No reply from Toyota; Description of Complaints: On March 19, 2021, I was driving my Rav4 (VIN[XXX] ) to go to Toledo Ohio. During the driving, the AWD System Malfunction/2WD Mode Engaged and the Engine Light c"
— Toyota Rav4 owner, 05/31/2021
Source: NHTSA Complaints Database
Most Reported Vehicles for P0456
Based on NHTSA owner complaint data.
| # | Vehicle | Reports |
|---|---|---|
| 1 | FORD FOCUS | |
| 2 | FORD ESCAPE | |
| 3 | FORD EDGE | |
| 4 | FORD FUSION | |
| 5 | FORD MUSTANG | |
| 6 | MERCEDES-BENZ E-CLASS | |
| 7 | VOLKSWAGEN PASSAT | |
| 8 | MERCEDES-BENZ C-CLASS | |
| 9 | CHRYSLER PACIFICA | |
| 10 | TOYOTA COROLLA | |
| 11 | NISSAN SENTRA | |
| 12 | KIA OPTIMA | |
| 13 | JEEP WRANGLER | |
| 14 | JEEP LIBERTY | |
| 15 | CHRYSLER 200 |
P0456 Reports by Vehicle
Detailed NHTSA complaint analysis for each vehicle model.
Diagnostic Tips
- Scan all modules, save freeze-frame data, and clear unrelated history codes before focusing on P0456.
- Confirm whether companion codes are present first; they often identify the root cause sooner than the headline DTC.
- Prioritize inspection around fuel/propulsion system and the most common failure path for this code family.
- Graph upstream vs downstream O2 sensor activity at warm idle and cruise; downstream should stay more stable than upstream.
- After each repair step, complete one drive cycle and verify readiness monitors instead of judging success after a quick idle test.
- If the code keeps returning on high-incidence platforms (for example FORD FOCUS), check TSB patterns and wiring/connector fitment before major part replacement.
Common Mistakes to Avoid
- ❌ Skipping freeze-frame review and losing the exact RPM/load conditions when the fault set.
- ❌ Installing a catalytic converter before ruling out upstream fueling/misfire conditions that can kill the new unit.
- ❌ Clearing P0456 and returning the car before monitors complete — this often creates repeat visits.
- ❌ Treating intermittent wiring or connector faults as permanent component failure without wiggle testing.
Frequently Asked Questions
Will I pass emissions with a check engine light on?
Can I just clear the code before emissions testing?
How much does a catalytic converter cost?
Reported Repair Costs for P0456
Based on 11 owner-reported repair costs from NHTSA complaints.
⚠️ These are owner-reported costs, not estimates. Actual costs vary by location, labor rates, and root cause. Source: NHTSA complaints database.
What To Do Next
Possible Fixes
- 🔧 Clean or replace EGR valve
- 🔧 Replace gas cap (EVAP codes)
- 🔧 Replace EVAP purge or vent solenoid
- 🔧 Replace catalytic converter
- 🔧 Replace secondary air pump or check valve
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1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
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Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.