Fix P0496 – Mechanic’s solutions that WORKED!

Trouble code P0496 Evaporative Emission System High Purge Flow means that there is too much air flowing to your EVAP canister, which increases the amount of fuel system fumes transferred to the engine.

P0496 quick overview

Meaning	P0496: Evaporative Emission System High Purge Flow
Is it serious?	This code is moderately serious and should be addressed soon to avoid potential fuel leaks and worsening fuel economy.
Possible causes	-Faulty or stuck-open purge valve -Faulty vent valve or solenoid -Damaged or loose fuel cap -Leaking EVAP canister or hoses -Electrical issues with EVAP sensors or wiring
How to diagnose?	Check Fuel Cap: Ensure the fuel cap is properly secured and undamaged. Inspect Purge Valve: Test the purge valve for proper operation using a multimeter and check if it is stuck open. Check for Vacuum Leaks: Use a smoke machine to find any vacuum leaks in the EVAP system. Test Electrical Connections: Inspect and test wiring and connections related to the EVAP system for damage or corrosion. Clear and Monitor Code: Erase the code and monitor if it returns after driving.

P0496 case study: What fixed the issue?

I looked into several P0496 cases to give you real-life examples of how this code is caused and what to do to fix it. The most common cause was purge solenoids or valves in the EVAP system. The faulty PCM was also an issue in some cases, so also consider this before setting your eyes only on the EVAP system. Check this P0496 solve cases:

P0496 chevy

Car: #1 2004 Chevrolet Express 1500 4.3L
Problem: P0442, P0496

Fix: The first thing the technician did was to look into fuel pressure. Pressure does look good and there is no drop in fuel pressure, so there shouldn’t be any fuel leaks. The customer said that he had a hard time starting the vehicle after putting the gas in. The issue was in the stuck-open purge solenoid which would allow fuel vapers to fill the intake, causing a hard start. Fixed by replacing the purge solenoid.

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Car #2: 2004 Chevrolet Tahoe LS 5.3L
Problem: Check engine, P0496

Fix: Again the same code and also Chevrolet but on a different car. The fuel pressure also didn’t suggest any fuel leaks and the purge solenoid was already replaced by 2 different shops, which didn’t solve the issue. The technician fixed it by replacing the solenoid again but for the OEM GM unit. Using the OEM part can solve the weird issue in a lot of cases, not just this code.

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Car #3: 2007 Chevrolet Suburban 1500 Z71 5.3L
Problem: Check engine, P0496, P0446, Can’t put almost any gas in the tank

Fix: The problem was hiding in the ventilation solenoid and the EVAP canister is full of gas. Fix was done by replacing the vent valve for the OEM GM unit and draining the canister. That fixed the issue.

P0496 Pontiac

Car: #1 2008 Pontiac G5 2.2L
Problem: Surge, Stall, MIL Lamp on, P0171, P0496

Fix: The technician couldn’t use Bi-directional tests to control the purge solenoid, not even after replacing it with a new unit. The suggestions were to check PCM -> EVAP wiring, which seemed to be OK, but reprogramming PCM fixed the issue.

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Car: #2 2007 Pontiac Grand Prix 3.8L
Problem: Stall, MIL Lamp on, Erratic Tachometer, P0496, P0016, P0171, P1819

Fix: After extensive testing of ECT, MAP, MAF, Purge Valve, Ignition Feed Circuits, and Engine Wiring Harness Circuits, no issues were found. Trying a new Crank Sensor and Ignition Module didn’t help. Replaced with 6 new Spark Plugs. Fuel Pressure stable at 60-63. The throttle body was cleaned and confirmed functional. The problem showed itself again after trying the PCM freeze test confirming it is a faulty PCM.