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Error Code P0467 is defined as Purge Flow Sensor Circuit Low. 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. It is, however, more common among Mercedes vehicles. Specifications on the definition, troubleshooting, and repairs, of course, 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 P0467 is set when the voltage at the sensor goes lower than the set level (usually below 0.3V) for too long a period of time. This code is commonly considered an electrical circuit problem.
Since this code is an electrical issue (not mechanical), it usually doesn’t lead to severe problems. Common symptoms will include the activation of Check Engine light and registration of the code to the system, and of course, increase in fuel consumption.
Common causes for this code include:
- Short to ground in the signal circuit to the PFS sensor
- Short to ground or open in the power circuit at PFS sensor
- Defective FPS sensor
- Failed PCM
How to Check
A better starting point for the diagnosis of this code is through using Technical Service Bulletin (TSB) and search for your particular vehicle. Sometimes vehicle manufacturer may have a PCM flash/reprogram that covers the problem.
Next, technicians check the flow sensor of the vehicle. The sensor is usually found mounted in the EVAP fuel system, also called as charcoal canister, which is located close to the fuel tank or maybe even on top of the fuel tank or fuel pump module. They inspect its wiring and connectors to look for problems, such as bare wires, burn spots, rubbing, scraping, or melted plastic. Then they pull the connector apart and check the terminals (metal parts) inside the connector. They will look for burned or green tint, which would indicate corrosion. Technicians use electrical contact cleaner and a plastic bristle brush to clean the terminals. Then they let it dry and apply electrical grease where terminals meet.
Then they will use the scan tool to clear the codes from the memory and see if the code comes back. If it does not come back, that means the problem was in the connections.
If the code comes back, technicians will proceed on testing the PFS sensor and all of its associated circuits. With Key Off, electrical connectors at the PFS are disconnected. Then, they will connect the DVOM black lead to the ground terminal at the PFS sensor wiring harness connector. The red lead of the DVOM is then connected to the power terminal of the PFS sensor wiring harness connector. They turn the Key On Engine Off and then check with the specifications set by the manufacturer. Voltmeter should read either 12V or 5V. If not, power, ground or PCM must be replaced.
If the vehicle passed the prior test, then the signal wire must be checked. With connector still disconnected, the technician will then proceed on moving the red lead of the voltmeter from the power wire terminal to the signal wire terminal. The voltmeter should now read 5V. If not, then signal wire must be repaired, or the PCM must be replaced.
If after all the repairs the code still appears, this would mean the problem is caused by a failed FPS sensor, though failed PCM should not be ruled out until the PFS sensor had been replaced.
How to Fix
- Repair or replacement of the short to ground in the signal circuit to the PFS sensor
- Repair or replacement of short to ground or open in the power circuit at PFS sensor
- Replacement of defective PFS sensor
- Replacement and upgrade of the PCM (rare)
Steps for diagnosis of this code may vary depending upon manufacturer, type of PFS sensor and wire colors.