Error Code P0465 is defined as Purge Flow Sensor Circuit Malfunction. This code is usually present with other system codes related to the EVAP control system.

This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, especially those made from 1996 up to the present day. It is, however, more common among Mercedes vehicles. Specifications on the definition, troubleshooting, and repairs vary from one make and model to another.


The PFS (Purge Flow Sensor) is usually found in the Evaporative fuel system, also called the charcoal canister, and located close to the fuel tank. In some makes and models, it is placed on top of the fuel tank or fuel pump module. This sensor works by converting EVAP system pressure into an electrical signal for the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes).

The PCM uses the signal to determine how much fuel it will have to send into the engine, along with the fuel entering the intake manifold from the EVAP system. Error Code P0465 is set when the input doesn’t match the normal engine operating conditions stored in the memory of the PCM, even for a second. It also checks the voltage signal from the PFS sensor to determine it is right at the initial Key On.

Error Code P0465 can be set due to mechanical (usually mechanical issue with the EVAP system) or electrical (PFS sensor circuit) issues. These factors must not be overlooked in the troubleshooting stage, especially if the problem is intermittent.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. The severity of the symptoms depends on the failure. If the problem is caused by a mechanical failure, the problem is most likely severe. If it’s an electrical issue, then it’s not as severe, as the PCM can compensate adequately for it. Common symptoms include:

  • Increase in fuel consumption
  • Other codes related to the EVAP system codes may be present

Possible Causes

  • Damaged fuel cap
  • Defective purge control solenoid
  • Cracked vacuum hoses
  • Cracked fuel vapor hoses
  • Clogged or damaged charcoal canister
  • Defective pressure or flow sensor
  • Damaged PCM (rare)

How to Check

Troubleshooting this code may vary depending on the manufacturer, FPS sensor type, and wire colors.

As with other error codes, diagnosis for this code starts with the use of OBD-II scanner; technicians use the scanner to verify the code and other codes that may be stored in the PCM, and determine what components are malfunctioning.

Next, technicians proceed their diagnosis by conducting visual inspecting of connectors and wirings related to the purge flow sensor circuit. If the issue is electrical data that is not what it should be, there’s a good chance the problem is caused by malfunctioning electrical components. The technician would then replace or repair any issues, and then clear the codes from the PCM before retesting.

If the code returns, the technician will then proceed to other repairs.

When diagnosing, it is important to clear the codes from the PCM and to retest the system at each step of the repair. This will help narrow down the exact cause of the problem, making the diagnosis and repair easier.

How to Fix

Common repairs for this code are:

  • Proper installation of fuel cap
  • Replacement of defective fuel cap
  • Replacement or repair of defective purge control solenoid
  • Repair, replacement, or unclogging of charcoal canister (if canister is necessary)
  • Repair or replacement of cracked vacuum hoses
  • Repair or replacement of fuel vapor hoses
  • Repair or replacement of defective pressure or flow sensor
  • Repair of faulty PCM (rare)

Error Code P0465 is not a serious problem, and it can be put off at your earliest convenience. However, since it causes increase fuel consumption, it should never be ignored.