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ajar70

2010 Rx 350

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I came home from work last week and parked the Lexus in the garage. We took our other car out for about 3 hours. When we returned, I was near the Lexus and heard the sound of a small engine running or fan noise coming from under the rear of the car. I crawled under and couldn't pinpoint it, but thought that the fuel pump may have been running. I started it up and ran for a minute or so, turned it off and it stopped.

I mentioned this to the dealer and their response was that they "couldn't replicate". Has anyone experienced this or have an idea what it is? Thanks.

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I noticed the same thing on my new RX 350. When I turn off the car the headlights stay on and that's where the motor noise is coming from. I suspect the motor used to swivel the headlights right/left in curves runs all the time. When the headlights turn off...the noise disappears (at least for me).

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I have experienced that same thing with our 2010 RX once. I am 99% sure it was the fuel pump. I thought it was unusual because most vehicles I am familiar with don't power the fuel pump relay unless the key is on. However, since you experienced it as well it may be normal with newer vehicle emission systems.

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I have experienced that same thing with our 2010 RX once. I am 99% sure it was the fuel pump. I thought it was unusual because most vehicles I am familiar with don't power the fuel pump relay unless the key is on. However, since you experienced it as well it may be normal with newer vehicle emission systems.

I think you're right on. I found this, which may explain it...

The evaporative control (EVAP) system captures any raw fuel evaporating from the fuel storage system (e.g. the fuel tank, the filler neck, and fuel cap). Under precise operating conditions dictated by engine temperature, speed, and load, the EVAP system purges these captured fuel vapors back into the combustion process.

System Overview

The Evaporative Control System is designed to not only capture, store and purge any raw fuel vapors that leak from any areas of the Fuel Storage System but also to run a series of self-tests that confirm or deny the Operational and Vapor Holding ability of the System. This is an important task because at least 20% of the Vehicle produced Air Pollution originates from malfunctioning Vehicle Fuel Storage Systems.

There are many ways for vehicles to 'leak test' the Evaporative System, but most perform the leak test either when the vehicle is sitting, say over night, or shortly after initial start up after the vehicle has been sitting over night. The Evaporative Systems operational performance is also tracked by the Power Train Computer by reading the change in the Oxygen Sensor voltages and Short Term Fuel Trim when ever the stored Vapors are released or 'purged' back into the combustion process. These values should indicate that fuel is being added to the system and that the over all mixture is getting richer. The purging process occurs when the vehicle is under acceleration, which is when most vehicles require additional fuel.

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I agree with the comments on the evaporative control and purge system operation, but that cannot explain the fuel pump running. The pump deals only with the liquid fuel and cannot influence the tank vapors to reduce or purge.

I have also experienced what sounds like the fuel pump running hours after my 2007 RX350 was last driven. The vehicles always runs fine.

On two occasions, I have found the battery down to a level of 'no crank' for no apparent reason of lights or accessories left on. Could it be the pump coming on? It has always shut off when I noticed it running, but I haven't stood there and waited for it. Anyone else experienced battery drain for no reason when they have also heard the sound?

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As a former dealership technician and field service engineer for GM I had to get to the bottom of this noise. Below is information I pulled from the Toyota Information System on the EVAP system operation. It's not the fuel pump, but the leak detection pump that is mounted right by the fuel tank. Bottom line - Normal.

1. Key-off monitor

This monitor checks for EVAP (evaporative emission) system leaks and canister pump module malfunctions. The monitor starts 5 hours* after the engine switch is turned off. At least 5 hours are required for the fuel to cool down to stabilize the EVAP pressure, thus making the EVAP system monitor more accurate.

The leak detection pump creates negative pressure (vacuum) in the EVAP system and the pressure is measured. Finally, the ECM monitors for leaks from the EVAP system, and malfunctions in both the canister pump module and purge VSV based on the EVAP pressure.

• The canister pump module performs a fuel evaporative emission leak check. This check is done approximately 5 hours after the engine is turned off. Sound may be heard coming from underneath the luggage compartment for several minutes. This does not indicate a malfunction. Pinpoint pressure test procedure is adopted by pressurizing the fresh air line that runs from the canister pump module to the air filler neck.

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As a former dealership technician and field service engineer for GM I had to get to the bottom of this noise. Below is information I pulled from the Toyota Information System on the EVAP system operation. It's not the fuel pump, but the leak detection pump that is mounted right by the fuel tank. Bottom line - Normal.

1. Key-off monitor

This monitor checks for EVAP (evaporative emission) system leaks and canister pump module malfunctions. The monitor starts 5 hours* after the engine switch is turned off. At least 5 hours are required for the fuel to cool down to stabilize the EVAP pressure, thus making the EVAP system monitor more accurate.

The leak detection pump creates negative pressure (vacuum) in the EVAP system and the pressure is measured. Finally, the ECM monitors for leaks from the EVAP system, and malfunctions in both the canister pump module and purge VSV based on the EVAP pressure.

• The canister pump module performs a fuel evaporative emission leak check. This check is done approximately 5 hours after the engine is turned off. Sound may be heard coming from underneath the luggage compartment for several minutes. This does not indicate a malfunction. Pinpoint pressure test procedure is adopted by pressurizing the fresh air line that runs from the canister pump module to the air filler neck.

The fuel system evaporative vacuum pump is powered 24/7.

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