Service message comes up - obviously a function of time not mileage since I have covered only 4900 miles since the last (50,000 @ 47,600) service but it has been a year so I planned to stop by the dealer and schedule (what turned out to be a 60,000 mile package inc. plugs & cabin air filter). The day before I planned to go in the CEL came on.

Service was scheduled - about a week hence and I was informed that the tab would be about $700! I was prepared to pay a bit more than with my usual very good independent mechanic (works for my brother-in-law) because the car is a CPO and I wanted to be certain that if an issue ever arose, there would be no maintenance questions but still..

Well, it turns out that a good chunk of that is the estimated time for dealing with the CEL - 190 minutes or 3 hours and 10 minutes. I can only assume that checking the CEL requires the use of a brand new code reader for each use and that reader is supplied in kit form which the mechanic must assemble before use!

The service advisor assured me that, so long as the light was steady, not blinking, I could continue to use the car. Being the cautious type, I was planning to stop by my brother-in-law's shop and have them pull to code to see what it was but it is probably now a moot point since THE LIGHT HAS GONE OUT!

 

Codes are stored so even if the light has gone out, the original code will be there. This is typical of things like the "loose gas cap" code. Fix your gas cap and the light goes off - but the code will remain. All the codes are OBD2 standards so your loaner from Autozone will view and clear the emissions codes but there are some proprietary codes that are more granular for diagnostics and there are codes from the other computers (ABS, TCU, Climate control, SRS etc ) that not all scanners will read. As a general best practice, if your car goes in for service with a CEL lit up, make sure you ask the tech to document the codes found for future reference. Not all codes point to a failed part... For example, I was doing a power steering fluid drain/fill on my wife's Highlander which required me to start/stop the car 5x in a very short interval, which set off the check engine light. I simply scanned/cleared the code and its not returned in 10K miles of driving...

 

The CEL can also be cleared with a code reader. It's a good idea to buy one, so you have it on hand. The next time you see the CEL come on, pull out your reader and see what the code is. I own three code readers - each does a little more checking. The cheapie ($25 on Ebay) is actually pretty good and tells me what the code is, then it allows me to erase it if I'd like. After erasing, it shows the monitors which have or have not cleared. If you have monitors that haven't cleared, you can't do a smog test - unless it's the Evap. At least that's the rule here in CA!

FYI, if you do have an evap code and you need to do a smog check, but don't want to fix the evap problem, there's a solution. Fill the tank, then clear the codes. Do the normal drive cycle required to clear the monitors. Everything but the evap will clear (as long as you keep 3/4 tank of gas in the car). The CEL won't turn on, because it won't run the evap test unless you have between 1/4 and 3/4 tank of gas. So the OBDII will show a ready for test condition, except for the evap, which is okay. You'll pass the smog test and as soon as you're below 3/4 tank and you're in the evap monitor mode, the CEL will come on. You should fix it, but you can get your tags (have the passed smog test) and drive your car until you have time to get it fixed.

 

Further to the above - stopped by my local "go-to" shop and they obligingly pulled the stored codes:

PO344 camshaft position sensor - faulty/missing signal
PO369 camshaft position sensor - circuit intermittent
PO171 system too lean
P3019 low coolant.

I looked at the coolant reservoir - cool engine - hard to read It's not full but not empty either.
I wonder if the "too lean" code could be related to the low fuel pressure sensor issue subject to a recent extended warranty notification.

 

yep low fuel pressure can cause the engine to run lean and throw a 0171 code. You can also look around for intake air leaks, vacuum line issues etc.

 

Apparently a faulty O2 sensor - replaced under CPO warranty