Technical > Automotive > Check Engine Light - Knows very little about cars

Check Engine Light - Knows very little about cars

At this point, lacking any detailed information about what the actual trouble codes were, I would recommend just driving it as usual, and wait to see if the light comes on again.

Some vehicles are sensitive to being overfilled, but I am not sure on your particular car. If TA63 checks in, we can get more detailed information on that.

To be honest, I'm not impressed with the response your chosen mechanic gave you. He should have been able to pinpoint the code source, and how old each code (if there was more than one) is in the system. The range of potential issues is about as broad as it can be. I would have been happy if he said "fuel system problem" or "catalyst problem" but not all of those...

Anyway, if it runs fine, has no other operational issues and the light stays off, you can dismiss it totally. If it comes back on, please find a different shop to perform proper diagnostics, and if you wish check back here with the results.

reply to weston631
There is no way putting another 55c in the tank set off the CEL. However you should check that the gas cap is on securely.

reply to weston631
Thanks a lot for the responses. I appreciate it.

The mechanic I went to that read the codes wasn't my mechanic. I've always used the Toyota dealer since 2003, but because I didn't want to wait all day at the dealer, I just brought it to the local shop and they read the codes for free, and reset the "Check Engine Light". It's now off, but I'm wondering when the CEL will come back on, if there is a real issue?

I tightened the gas cap prior to having the CEL reset, but it seemed like it was tight already. It was night time and hard to see.

If there is a real issue, would the CEL come back on after driving 100 miles, 200 miles, etc? Thank you so much!!

If the light comes back on, then yes, it needs to be addressed. As I noted, a proper diagnostic needs to be completed that will isolate the nature of the problem.

As far as when it will come back, that is up to the situation at hand; No problems present to cause the light to come on again, then it won't be back on at all, at least for that particular problem. The more significant the issue, the faster it comes on. For example, an engine misfire that is detected will immediately cause the light to come on, and if it is a persistent misfire, the light will actually flash to signify "take care of this NOW!". This is because a persistent misfire condition can cause damage to the catalytic converter, as well as cause excessive tailpipe emissions in the form of raw, unburned fuel.

Other problems that are less critical and non-damaging may take several "detection cycles" to set a trouble code and turn on the light. If the problem is detected over a certain number of start-stop cycles, or for a certain length of time, it will come on. Then there are codes that will be set in the computer but don't cause the light to come on at all. Typically these will be body-control module issues, and some drivetrain scenarios that are out of range. They are detectable only when a technician performs diagnostics, and then they can be addressed if needed.

There's a quick and basic explanation of the Check Engine Light display strategy.

reply to weston631
gas caps are fairly cheap so if it turns out to be that than its a minimal issue.

Is it mission critical though is what I wonder. As in if someone never fixed the gas cap would the car be harmed? as in does the gas tank have to be kept at a positive pressure?
--
[65 Arcanist]Filan(High Elf) Zone: Broadband Reports

reply to Kearnstd
Since the CEL was reset a few days ago, I drove about 200 miles and maybe turned the car on/off 20 to 30 times.

The CEL has not come on again yet. Is that a "good sign" or do I still need to give it more driving cycles and more miles?

Thank you so much!!

Sounds like it was just a loose gas cap.

Now you know which mechanic NOT to go to!

reply to Bob

You also fail if the check engine light is on, or if the car's diagnostic port indicates a problem with the gas cap.

Update:

The CEL came back on (after about 250 miles and a few days) so I brought it to the Toyota dealership.

They said the code was P0420. (Catalyst System Efficiency Below Threshold)

I just passed inspection a few weeks earlier (before CEL came on) but they said it was just a "coincidence" it happened right after.

Is it safe to drive with this issue for several months? I'm not due for another inspection for several months and before next inspection, I rather buy a new car. I already put a lot of money into the 2003 Corolla.

They quoted me about $1700 for the new catalytic converter and “reflashing the computer”, which is also needed.

While I certainly don’t want to add to the pollution, from a mechanical point, is it perfectly safe to drive for many months and many miles?

Thank you so much!!!

reply to weston631
Check an independent shop; $1,700 is a lot for a cat. That's what the 4 cats on my mustang cost to get replaced at the dealer.

I paid about $250 for a generic one on one of my cars at a muffler shop.

It is safe to drive. Sounds like the cat is getting fouled or the catalyst is flaking off.

Is it burning oil? That can plug up a cat.
--
Scott Henion

Embedded Systems Consultant,
SHDesigns home - DIY Welder

reply to weston631
Your Toyota Camry use's a heated oxygen sensor with a service life of about 100,000 miles
I'd bet the internal heater circuit in the O2 sensor isn't working right
The sensor can't produce and send the rapidly toggling voltage signal till its above 600 F
So without the heater it only works right some of the time
The OBD II system monitors converter efficiency by comparing the upstream and downstream oxygen sensor signals
O2 sensor is easy enough to check but if you have 155,000 miles on them I'd replace both
as a Regular normal car maintenance item and with a Toyota Corolla clean the mass air flow sensor
also Try a different brand of Gas then go from there it is perfectly safe to drive

reply to weston631


For sure I would suggest a second estimate, but do NOT settle for a cheap "universal fit" replacement converter. There are high-quality aftermarket converters available, and make sure you specify that or you will have other problems down the road.

It is not going to give you any operational issues in the near future, but it would be best to make the needed repairs as soon as you are able to do so.

reply to PoloDude
Actually on a Toyota, it can, but it has nothing to do with the OPs O2 sensor. When you overfill some Toyotas. For example my 2000 Corolla, the charcoal canister can flood and the solenoid that tests the gas cap gets gummed up. Next drive cycle will result in a CEL.

reply to spud

reply to weston631
I had a check engine light go on. I have a Dodge so was able to get the code off of the odometer.
Turns out the gas cap had a bad seal.

If you have a pepboys or advanced auto, go to them to get the code.
I find it interesting the repair place didn't "keep" the code and let you know what it was.
--
Is a person a failure for doing nothing? Or is he a failure for trying, and not succeeding at what he is attempting to do? What did you fail at today?.

reply to weston631