Are check engine/error codes saved?

[bsannich]

I did a search, but couldn't find this particular question. Sorry if this has been asked before.

I have an appointment for my '18 this morning for a check engine light that came on last weekend. The light came on, the engine was immediately sluggish, and I received text/email form OnStar telling me to bring it in to get the emissions system checked. I turned it off and turned it back on, and the issue repeated itself after a short time.

Unfortunately, this has happened several times before and I was told that when the light is off, the problem disappears and there is no trace of it. Eventually, after 3-4 trips to the dealer, they were finally able to diagnose it and it needed a new injector. But I got the runaround several times before it was fixed. It was a huge hassle because I obviously never knew when it was going to happen.

(For them to finally find the issue, I had to bring it there with the light on. I was working an hour away from the dealer and literally drove right there and refused to turn the engine off until they diagnosed it.)

I have a feeling they're going to tell me the same thing this morning - that the condition is not currently present, and they have no way of troubleshooting it without the light actually being on (i.e. that the error codes are not saved in the ECM). I find that extremely hard to believe, since even my old 1991 Camaro stores codes.

Can anyone shed light on this? Are error codes "saved" and retrievable at the dealer if no longer present?

Thanks for your help.

 

[wjburken]

Many of the codes will be saved as historical codes for this purpose.

Did OnStar tell you what the code/codes were?

 

[OR VietVet]

Many of the codes will be saved as historical codes for this purpose.

Did OnStar tell you what the code/codes were?

Like @wjburken said, history is available and if On Star said to go in for inspection, then they have a history of the code as well. If I was you, I would get at least a code reader that you can plug in when the problem appears and the light is on and then get the code and write it down but DO NOT clear the code. Any dealer should work with the vehicle owner to help facilitate an inspection of the problem and at least be able to check for TSB's and that ON Star record of the event is very key to them not getting away with "sorry, can't duplicate or check without light on at this time" crap.

 

[Bill 1960]

The answer unfortunately is “it depends”. Some codes are stored until manually cleared, others clear themselves automatically if the fault condition ceases to exist. So unfortunately, without knowing what specific code is involved indications are yours is transient.

You can always stop in at any convenient auto parts store when the condition exists and they’ll read the code for you. Then you’ll have independent confirmation if you don’t fully trust the dealer.

 

[OR VietVet]

I think some history codes are cleared after enough ignition cycles go by without another fault happening to set that same code.

 

[Tonyrodz]

I'd get a code reader to read the code, then take a pic of it. Imo much better then writing it down.

 

[Joseph Garcia]

^^^^^ A code reader that meets your budget should be a part of your tool box. It will save you literally thousands of dollars over the life of your truck.

 

[OR VietVet]

I'd get a code reader to read the code, then take a pic of it. Imo much better then writing it down.

^^^^^ A code reader that meets your budget should be a part of your tool box. It will save you literally thousands of dollars over the life of your truck.

Even though I bought a Tech 2 I still have and will never get rid of my NAPA brand code reader that is in my rig at all times. I got it for less than $60 over 8 years ago and works flawlessly and I have helped friends with reading codes at the American Legion and VFW I belong to. No more do they have to take to a parts store and be talked in to buying a part because the code says, "This part is bad". That is ******** a lot of the time.

 

[drakon543]

i agree with all statements above but i would like to add 1 part in defense of mechanics. dealerships are stealerships however unless a code is very specific most codes will only point to an area or symptom not the cause. an injector causing an emissions fault would definitely be one of those cases. even if they pulled the code from history without having a live data scan atleast of the moment in question pin pointing the issue is sometimes impossible. however against the dealership what they should have offered is a loaner and told you they were going to run it around and try to duplicate the problem. the history should show the ecm is seeing a legitimate problem so instead of just giving it back they should have kept it until they found the problem.

 

[RobDenali]

tell them you smell fuel after a cold start, even if you dont. They will test all the injectors or at least one side depending on your codes