Stupid Check Engine Light Keeps coming on - 2003 RX300

[red baron]

Just curious, what kind of car was this?

Nissan Pathfinder 2004

[cyrus buelton]

Thanks guys for all the good advice.

The oddest thing is when I started running 87 octane, the damn light came on.

Prior to that, I was running 89 and no issues.


I have no issue with getting the issue resolved, but it always happens about a day after I fill it up.

My mileage has not suffered as a result of this, so I don't think it is an O2 sensor, which is a common cause for that stupid light to come on. But again, nobody has mentioned that on here, so I am just speaking from experience on other vehicles.


I'd just prefer an easier solution as the Lexus Dealer charges 85$ just to run the diagnostic on it.

[Sinister]

Check that blinker fluid, man. 

[cyrus buelton]

Check that blinker fluid, man. 

We can also talk about the mysterious light that is illuminated that tells me I have a rear brake light out too.

All are fully functional.

[Porsche Monkey]

Thanks guys for all the good advice.

The oddest thing is when I started running 87 octane, the damn light came on.

Prior to that, I was running 89 and no issues.


I have no issue with getting the issue resolved, but it always happens about a day after I fill it up.

My mileage has not suffered as a result of this, so I don't think it is an O2 sensor, which is a common cause for that stupid light to come on. But again, nobody has mentioned that on here, so I am just speaking from experience on other vehicles.


I'd just prefer an easier solution as the Lexus Dealer charges 85$ just to run the diagnostic on it.

There are quite a bit of different things that can cause a check engine light to come on.  In your case it sounds like the evaporative emissions system.  In that system there are a handful of things that can fail and cause the light to come on.  The code that Autozone pulled just points a tech in the general direction.  It is in no way saying "replace that part right there".  This is where an experienced Lexus Technician comes into play.  He has to decipher the code and start looking for problems.  Whenever a code is stored, there are pages of data that get stored with it.  It's going to be Japanese to that autozone guy and maybe rough spanish to the general service tech.  Take it to the dealer where the techs there are familiar with the car and have most likely seen the problem. 
If I was to take a shot in the dark I would say you have a fuel tank vent valve problem, or a carbon canister purge problem because you say the light comes on after you fill up.  Both those systems need to be checked before an accurate diagnosis can be made.  There is a reason the dealer charges you to diagnostic time vs autozone doing it for free. 

[cyrus buelton]

Thanks Ducaholic for the advice.

I am going to get this resolved, but I am pretty busy the next several weeks.

Is this hurting my vehicle to drive with it on?

[metallimonster]

It shouldn't hurt the car at all.


The check engine light only comes on for Emissions Reasons.  The only time you should actually worry is if the check engine light flashes which means it is misfiring but you would probably notice by it running like shit and shaking. 

We used to send cars out with CELs all the time while we were waiting for parts.

[cyrus buelton]

I figured it wasn't hurting anything, the owner's manual says if it is flashing (like you suggested) to take it in.



Got the check engine light on in the Jetta too. I think the coolant level monitoring sensor is bad or something ridiculously stupid like that.


make the beast with two backsing cars



Guess I should have bought a Chevy like Sinister said

[Porsche Monkey]

It shouldn't hurt the car at all.


The check engine light only comes on for Emissions Reasons.  The only time you should actually worry is if the check engine light flashes which means it is misfiring but you would probably notice by it running like shit and shaking. 

We used to send cars out with CELs all the time while we were waiting for parts.

+1. If the light is not flashing your okay.

[redxblack]

Could it be summer blend gas? My CEL comes on when I fill up at a certain filling station, but not when I go to more reputable petrol dealers. I use 87 across the board, but some stations always give me a CEL until the tank is empty and I refill at the Marathon down the street from home.

[metallimonster]

Got the check engine light on in the Jetta too. I think the coolant level monitoring sensor is bad or something ridiculously stupid like that.

make the beast with two backsing cars

Guess I should have bought a Chevy like Sinister said

It's probably the coolant temp sensor.  Those things are notorious for going bad.  Makes the ECM think it is running colder than it is which richens the fuel mapping.

[cyrus buelton]

It's probably the coolant temp sensor.  Those things are notorious for going bad.  Makes the ECM think it is running colder than it is which richens the fuel mapping.

Yup!

that's exactly what it is. The wife picked it up from the dealer after a servicing, so she remembered what it was.


Is that easy to change out?

[cyrus buelton]

Thanks Jay (metallimonster)!

Got all my "warning" lights to go off.


Not sure all would agree, but his advice has worked for 15 miles of driving through our email conversations.