Fix P0497: Mechanic’s solutions that WORKED

The code P0497: Evaporative Emission System Low Purge Flow indicates a fault in the vehicle’s Evaporative Emission Control (EVAP) System, pointing towards an issue where the system is not purging the vapors as it should. Most commonly, this is due to a problem with the EVAP Canister Purge Valve or associated wiring.

P0497 quick overview

Meaning	P0497: Evaporative Emission System Low Purge Flow
Is it serious?	It can lead to increased emissions and may cause the car to fail emissions testing. Over time, it could potentially cause issues with fuel efficiency or engine performance.
Possible causes	– Faulty Evaporative Emission (EVAP) Canister Purge Valve – EVAP Canister Purge Valve harness is open or shorted – EVAP Canister Purge Valve circuit poor electrical connection – Faulty Fuel Tank Pressure (FTP) Sensor – Clogged or disconnected EVAP system hoses – Charcoal canister damage, especially from impact or aggressive conditions – Incorrectly installed wiring or reversed wires at components
How to diagnose?	Inspect wiring and connectors: Check for proper connection and condition of wiring. Test sensor voltage: Confirm that sensors like the FTPS have correct voltage readings. Check purge valve: Inspect the EVAP Canister Purge Valve operation and for any clogs. Use a vacuum pump: If applicable, use a vacuum pump to test purge control solenoid functionality. Review technical bulletins: Look for manufacturer service bulletins for known issues. Perform battery voltage test: Utilize a 1.5V battery test on sensors to check signal response.

How to fix P0497 – learn from mechanics

I looked into P0497 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Honda

Vehicle Information 2004 Honda Civic LX 1.7L with the MIL Lamp on

Issue + Repair History

• Code P0497: Evap low purge flow.
• Previously replaced the evap canister vent shut valve.

What Are People Suggesting to Fix Issue

• Check the purge valve for proper flow.
• Inspect for a faulty purge flow solenoid.
• Look for kinks in the pipe to the canister or insufficient vacuum from the engine.
• Use live data to check the fuel tank pressure sensor reading.
• Check the evap hoses and tubes for clogs or nests.
• Perform an Evap-function test to monitor tank pressure and purge valve performance.
• Test the purge valve for proper flow and vacuum maintenance.

What Was the Final Fix The final fix was replacing the Purge Solenoid located next to the throttle body because it was not allowing enough vacuum flow through it.

Case #2: Volvo

Vehicle Information 2003 Volvo S60 2.4T 2.4L Evap

Issue + Repair History

• ECM-4007 eVAP system: Signal Too Low.
• Code P0497: Evap system low purge flow.
• Customer replaced purge valve and leak detection pump with aftermarket units to pass smog.
• Aftermarket leak detection pump had an air leak, replaced with an OE unit.
• No previous repair history mentioned.

What Are People Suggesting to Fix Issue

• Check vacuum hose from manifold to purge valve for leaks, especially above the starter.
• Look for hose restrictions, not just leaks, since the ECM doesn’t detect a mixture change during normal purge.
• Inspect hoses under the manifold and the line from the purge valve to the back of the car for damage or pinching.
• Use an OEM purge valve instead of aftermarket if problems persist.
• Control the purge valve with a scan tool to check ECM circuit integrity and valve operation.
• Bench test the new purge valve to ensure it is opening fully.
• Make sure the line from the back engine to the tank is not pinched and not restricted.

What Was the Final Fix The check valve under the intake manifold was installed backwards. Correcting this resolved the issue.

Case #3: Mercedes

Vehicle Information 2008 Mercedes-Benz S550 5.5L

Issue + Repair History

• Difficulty setting readiness monitors; P0301 code for misfire on cylinder 1 appeared after attempting to set.
• Low compression across all cylinders, but especially on cylinder 1.
• The vehicle has good acceleration despite low compression and uneven idle.
• Previously replaced plugs, coil on cylinder 1, both right magnets, and repaired purge hose (P0497).
• Misfire resolved by replacing the fuel injector on cylinder 1.

What Are People Suggesting to Fix Issue

• Low compression readings suggest a worn-out engine.
• Check for carbon buildup on intake valves and runners.
• Perform a leak down test for more accurate assessment of engine condition.
• Inspect intake manifold gaskets for leaks.
• Reset cam timing adaptation values with a Star Diagnostic computer.
• Caution against running the engine with a coil disconnected to prevent damage to the ECM.

What Was the Final Fix The constant misfire on cylinder 1 was resolved by replacing the fuel injector on that cylinder. After the replacement, the fault counter showed zero misfires and the vehicle was able to run 15 miles without any pending fault codes. The readiness monitors are expected to take more time to set due to the nature of the vehicle, and the customer was informed accordingly. It was also noted to never start the car with a coil off the plug to avoid frying the coil and potentially damaging the ECM.

Case #4: Honda

Vehicle Information 2004 Honda Civic Hybrid 1.3L

Issue Trouble code P0497 indicating an EVAP system low purge flow.

Diagnostic Steps Performed

• Checked for FTPS (fuel tank pressure sensor) voltage; found it to be 0.0 volts on live data.
• Confirmed the sensor itself is good; correct voltage when back pinned at the sensor and at the ECM.
• The 5-volt reference to the sensor is good.
• Verified with a second scan tool that the ECM is receiving a 0.0 volt reading from the sensor despite it receiving the correct signal voltage.

Suggested Fixes

• Check the purge control solenoid as it may stick closed; use a vacuum pump and bidirectional control if available to test the solenoid.
• Supply a 5-volt supply directly to the sensor wire to check if the ECM can see a change in voltage.
• Use a 1.5-volt AA or AAA battery to apply voltage directly to the signal wire for testing, a trick for verifying voltage signal integrity.

Without reported fix

Case #5: Honda

Vehicle Information 2004 Honda CR-V EX 2.4L

Issue MIL Lamp on, with codes P0134 and P0497.

Diagnostic Steps Performed

• Previous shop provided codes but did not conduct repairs.
• Found and repaired damage to the emissions canister assembly.
• Reconnected lines to the fuel tank and replaced a broken purge solenoid with an OEM part.
• No codes found after initial road test post-repair.

Resolution Steps

• Corrected reversed wiring on the pressure relief valve on the canister which resolved one of the codes.
• O2 sensor signal output and return voltage were verified to be correct.
• Replaced the O2 sensor, which resolved the code associated with it.

Additional Comments and Suggestions

• It was suggested to check for charcoal contamination of the purge line if the canister had suffered impact damage, as this could cause low purge flow and trigger the P0497 code.
• A recommendation was made to review a specific service news bulletin that details the condition and repair process for issues related to aggressive off-roading that could lead to wiring and emission component damage.
  
  FIX Report Summary
• The technician resolved the diagnostic trouble codes on the vehicle by taking the following steps:
• Upon receiving a fax from the dealer, the technician discovered that the wires on the pressure relief valve of the canister were reversed. After correcting the wiring, the evaporative emission system low purge flow code (P0497) did not return.

Advice	Brief Description of Diagnostic Step
Check and correct wiring	Ensure that all connections, especially at the canister and sensors, are correctly installed and not reversed.
Verify sensor functionality	Conduct tests to confirm that sensors (like the O2 sensor and FTPS) are working properly and giving accurate readings.
Use alternative testing methods	Utilize simple tools like a 1.5V battery to test sensor response, which can help isolate the problem.
Confirm ECM/PCM is receiving correct signals	Double-check if the vehicle’s computer is getting the correct voltage signals from the sensors using back probing methods.
Refer to technical bulletins and manufacturer data	Check manufacturer’s service bulletins and wiring diagrams for known issues and proper wiring configurations.