Check engine light came on and has the code P0446 for a 1999 Lexus RX300. What should I do first?


Asked by Nagle423 Sep 05, 2013 at 03:08 PM about the 1999 Lexus RX 300 AWD

Question type: Maintenance & Repair

I just bought a 1999 Lexus rx300
2 days ago and I took my sister for a
ride in it the night I bought itand I drove over a speed
bump going very slow and next thing
I know the check engine light is on. I took it to an auto part store and they said the code is a P0446 and they dont carry the part so I need to go to the Lexus dealership. I was hoping there was something I could do first to see if I can fix it. Someone said it may be the wrong size gas cap? I dont have a warranty and am hoping this will not be an expensive fix!

8 Answers

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction There will be no obvious symptoms to driver, other than Malfunction Indicator Lamp (MIL) illumination. Causes A code P0446 could mean one or more of the following has happened: Faulty vent valve Open, short or excessive resistance on Vent valve control circuit Blockage of vent valve Bad PCM Possible Solutions With a P0446 OBD-II trouble code, here are some things to try: Replace Vent valve Repair open, short, or resistance problem in control circuit Repair open, or short, or resistance problem in power circuit Replace PCM

10 people found this helpful.

Doesn't look like a DIY Nagle. But not a MAJOR expense

4 people found this helpful.

From another site: It very well could be your gas cap. Missing Fuel cap - Incorrect fuel filler cap used - Fuel filler cap remains open or fails to close - Foreign matter caught in fuel filler cap - Vent control valve harness is open or shorted - Vent control valve circuit poor electrical connection - Faulty vent control valve

11 people found this helpful.

Happened to me on my RX300. Vacuum hose on the back of the air filter box was not replaced after the air filter was replaced. I have it on again so hopefully an easy fix. Also, the check engine and vsc lights don't come on until about 100 miles after the hose was disconnected. Very common.

12 people found this helpful.

Just had the little engine light come on, checked gas cap it wasn't tight at all, manual says drive 3 times to make it go away, if not get checked at Midas or something.

4 people found this helpful.

Engine light came on 1999 RX 300 with 103K miles. First I was losing two spark plug distibutors as engine was missing. Purchased 6 online for $99.00. Changed those out, very simple and quick. Also after changing them out the overdrive would not wok. Read up and was informed that all sorts of things could be wrong. I fixed the problem. Her is how! First: Cleaned air mass sensor located at the top back of the Air cleaner box. (Ten minutes). As the engine was running smotthly like new) but overdrive was still not working I disconnected the battery. This re sets the computer. I recoonected the battery after 30 minutes and the problem was solved. Toyota or lexus would likely charge you $500 for the two condensors and could also tell you all sorts of other things need fixing. Try these fixes first before taking the car in. David

6 people found this helpful.

Crazy thing I bought a 99 lexus 300 rx and second day I drove threw a park went over a few speed bump slowly and noticed on my way out the engine light was on. I was like great . I came across this write up and I'll see what I can do


2002 300 rx in the family since new high mileage runs like new. only issue is crack in the fuel tank. No leak or smell if fuel is kept below half full. check engine light has been on (not blinking) for the last two years.

2 people found this helpful.

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