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P0468 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0468 is an OBD-II Code that is triggered when the Purge Flow Sensor Circuit High Input goes out of range or detects a failure.

Meaning

A P0468 code is the result of the ECM (Engine Control Module) receiving a signal indicating an issue with the purge flow sensor including communication with the PCM. The purge valve, gas cap, fuel lines, pressure and flow sensors, wiring, hoses, connectors, vacuum lines, or the fuel tank may also be faulty.

Causes

Common causes for this code include:

  • A gas cap that is installed incorrectly
  • Hoses that are cracked or broken due to fuel vapor or vacuum leaks
  • If you have a clogged or broken charcoal canister,
  • The purge control solenoid may be defective.
  • A pressure or flow sensor has malfunctioned.
  • PCM (Powertrain Control Module) failure (very rare)

Symptoms

Symptoms of P0468 can include any or all of the following:

  • Engine Light ON or Service Engine Soon lamp is lit
  • MIL – Check Engine light comes on
  • Codes are triggered, including P0468
  • Check engine, VSC, and TRAC lights illuminate
  • Rough idle when the vehicle has been running for a while. The engine may shake and sputter. It may die at idle speeds if the code isn't addressed immediately.
  • Failures to accelerate normally when the throttle is depressed

Diagnosis

To diagnose a P0468 DTC code, an automotive technician would:

  1. Check the codes of the MIL (Malfunction Indicator Light) with an OBD II scanner
  2. Record any present DTCs
  3. Look up the code on this site, or others like it
  4. Verify that there are no other codes present before diagnosing the vehicle for P0468 only
  5. A good place to start if you have a P0468 would be to inspect all areas of leakage in and around your fuel tank and system components. These can include vacuum lines, fuel hose connectors, along with connectors on all the various sensors involved in your EVAP system (the pressure sensor or flow sensor). Remember that even small leaks can contribute to this failure, so ensure a thorough inspection.
  6. A fuel cap that is not properly installed or has cracks in it can also cause a P0468.
  7. Inspect for any other DTCs
  8. Check the sensors and lines, replacing them if there are any issues
  9. Repair as necessary
  10. Reset the codes and observe your vehicle to see if the code returns or if other problems arise
  11. If all other causes have been exhausted, inspect the PCM (Powertrain Control Module) for an internal fault CPR (Customer Part Return) should be used to send off a PCM for testing if it cannot be inspected ourselves. This is because no code will currently show up on a scan tool since this issue doesn't happen while driving normally, only when the problem has been triggered.
  12. Once the PCM is tested and repaired if necessary, reset the codes and observe your vehicle to see if the code returns or if other problems arise
  13. Reinstall all components and test drive the vehicle to ensure proper operation of all parts and accessories.

Common mistakes

  • The following are common mistakes when diagnosing the trouble code P0468:
  • Failing to check all of the EVAP system components for leaks or damage
  • Failing to verify the gas cap is installed correctly and is not damaged
  • Failing to inspect lines, sensors, and other fuel system components for damage or defects 
  • Failing to check vacuum and pressure lines for ruptures or abnormalities such as kinks in the line
  • Assuming that a PCM failure will always trigger a DTC, even though this is not true
  • Not having a thorough understanding of how the EVAP system operates and why it fails can lead you to assume some incorrect causes or symptoms, which could result in significant delays in diagnosing and repairing your car.

How serious is this?

A car with a P0468 trouble code is most likely to have an issue with the gas cap, but many other issues can cause this code.

The diagnostic trouble codes are divided into three different categories by the Society of Automotive Engineers (SAE): 

  • Code Category B: The vehicle is drivable and may or may not exhibit the particular symptom
  • Code Category C: The vehicle is not drivable and the particular symptom is present
  • Code Category D: A combination of C & B ("D" stands for "debility")

A P0468 is categorized as a C-type trouble code, which means that it applies exclusively to vehicles that are able to run normally. This means that it doesn't apply to cars that turn over but will not start, or to cars that have a drivability issue but will not accelerate.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Replacement of the PCM (Powertrain Control Module)
  • Replacing vacuum lines, sensors, and other EVAP components known to have defects or leaks
  • Cleaning or replacing the gas cap so that it is free of damage or defects
  • Verifying all connections are secure and not damaged before reassembling the vehicle 
  • Repairing any additional DTCs present

Related codes

A P0468 is related to these codes:

P0442 – Evaporative Emission Control System Incorrect Purge Flow (returns immediately after clearing)

P0446 – Evaporative Emission Control System Leak Detected (very small leak) 

P0441 – Fuel Vapor Emission/Supply System Malfunction 

Related DTC only in the presence of a "B" type code, meaning that when another code is present, this code will always be present. It means that there is a very small leak somewhere in the system.

Low Pressure in Fuel Tank or Filling Station

PNF-0718C Low Pressure in Fuel Tank or Filling Station - A 

P0458 - Evaporative Emission Control System High Purge Flow - An excessively high amount of fuel has been purged in a "C" type code. This usually means that the gas cap was loose or missing and that pressure built up in the fuel tank, which then caused the PCM to activate the EVAP system to release that pressure.

How much does it cost to fix the P0468 code?

The repair cost of a P0468 code is determined by the type of car you have and how extensive the repairs are. A PCM replacement on a more recent model vehicle may be expensive, while extremely inexpensive on an extremely old vehicle. If there are no other DTCs present, then this code may not require any further repairs at all. The average cost for diagnostics and repairs of a P0468 is $84.99.

Conclusion

In conclusion, the P0468 is a trouble code that indicates a problem with the EVAP system. If your car has this code present, there is a strong chance that it means that your gas cap needs to be replaced. Other issues such as cracked parts in the EVAP system, leaks or ruptures in vacuum lines and sensors can also cause this code. Replacing these components and re-inspecting them may fix the issue, but replacing the PCM will resolve all issues if it is defective. This information should be used as guidance only; an expert mechanic should always be consulted before any major repairs are made to a vehicle's systems.

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