Engine Light Coming on....Very strange

[TNJYOUNG]

Good morning fellow Tahoe/Yukon owners. I have a 2013 Tahoe with just over 120K miles. I bought it with ~85k miles on it and I have owned it since. At about 100k miles I filled the tank with 93 octane, 100% (no ethanol) gasoline. I have always had the practice of running a tank of "super unleaded" occasionally through any vehicle that I have owned.

Within about 100 miles of filling up my "check engine" light came on so I stopped at a local Auto Parts store to have them hook up their diagnostic computer to read my codes. The code read "oxygen sensor" at the catalytic converter Bank #1 or Bank #2 or something like that. Thinking it needed this part, I contacted the dealer than they gave me a price on replacement. The price was pretty high and I remember thinking "yeah, it probably needs this, but I just filled up with a different gasoline, too, so this is odd"

So I drove out that tank of gas, engine light on the whole time, and stopped to fill up again. This time I filled up again with the cheapest 87 octane (with up to 10% ethanol) gas that I could find. I drove off and within 30 miles the light went off. The light stayed off for over 1.5 years.

This past weekend I took a road trip and was about 100 miles away from home and needed gas. I pulled in to get gas and I don't know why, but I filled up with 93 octane (100% no ethanol) gas again. Same story as before. By the time I got home, the check engine light was on and the first start in the mornings felt a little rough.

Also, like before, I ran out that tank of gas and filled up with the cheapest 87 (with ethanol) that I could find. Also like before the engine light went off and the truck is running smooth again.

Anyone else experience this strange phenomena?

 

[OR VietVet]

This is like when you go to the doctor and tell the doctor that when you raise your left arm up to your shoulder it hurts. Then the doctor looks you in the eyes and says, "Well, don't raise your arm up there then". Someone will likely know why but I don't but the story is interesting. What does your owner's manual say about the type of fuel that is recommended for the engine?

 

[Fless]

I think it would be incredibly helpful to know which specific code is setting the CEL.

 

[OR VietVet]

Yep, they assign code NUMBERS for a reason, huh.

 

[TNJYOUNG]

This is like when you go to the doctor and tell the doctor that when you raise your left arm up to your shoulder it hurts. Then the doctor looks you in the eyes and says, "Well, don't raise your arm up there then". Someone will likely know why but I don't but the story is interesting. What does your owner's manual say about the type of fuel that is recommended for the engine?

LOL! You are right! Owner's manual simply states 87 octane or higher.

 

[TNJYOUNG]

I think it would be incredibly helpful to know which specific code is setting the CEL.

I had the codes pulled the first time this happened in late 2018 and I no longer know what codes they were. I did not have the codes pulled this time.

 

[PG01]

0420 and or 0430 probably. Your o2sendors not liking the super gas. Unless the engine is tuned I would stick with 87

and yes, every few years i get same codes in my 13 hoe but i use 91-93 all the time...

edit: sorry, it is probably 015b or 015d delayed response from either 02 sensor

 

[TNJYOUNG]

0420 and or 0430 probably. Your o2sendors not liking the super gas. Unless the engine is tuned I would stick with 87

and yes, every few years i get same codes in my 13 hoe but i use 91-93 all the time...

edit: sorry, it is probably 015b or 015d delayed response from either 02 sensor

Thank you. Yeah, my truck doesn't have the green "Flexfuel" logo on the back, but I often wondered if these things were made to work well (better) with a little corn in the gas? Thank you for letting me know that I am not the only one getting codes like this occasionally.

 

[PG01]

 

[PG01]

Thank you. Yeah, my truck doesn't have the green "Flexfuel" logo on the back, but I often wondered if these things were made to work well (better) with a little corn in the gas? Thank you for letting me know that I am not the only one getting codes like this occasionally.

But if its a 13 and the gas cap is yellow its flex fuel

 

[wjburken]

All good points mentioned already.

One other thing is at 120K on the clock, have you changed the plugs since you have owned the vehicle? Also, when was the last time you cleaned the MAF sensor?

 

[TNJYOUNG]

But if its a 13 and the gas cap is yellow its flex fuelView attachment 247884

I will check in a few minutes. I honestly can't remember what color the cap is. Funny after hundreds of fill-ups, I don't have a clue.

 

[TNJYOUNG]

All good points mentioned already.

One other thing is at 120K on the clock, have you changed the plugs since you have owned the vehicle? Also, when was the last time you cleaned the MAF sensor?

Well, honestly, I do not have any idea what an MAF sensor is, where it is located, or know how to clean it.

As for the plugs, they have never been replaced to my knowledge. I have been meaning to look at how hard the job would be, what wrench (socket) I need, and do the job. I have not changed plugs since my teens, but I have done it a few times.

Edit: I have now watched videos on both and will plan to do them soon. Any tips on tools needed for the spark plug change would be much appreciated.

 

[wjburken]

Well, honestly, I do not have any idea what an MAF sensor is, where it is located, or know how to clean it.

As for the plugs, they have never been replaced to my knowledge. I have been meaning to look at how hard the job would be, what wrench (socket) I need, and do the job. I have not changed plugs since my teens, but I have done it a few times.

The MAF is the Mass Air Flow sensor. It is located just outside your airfilter housing in the intake tube. It measures the amount of air coming into your engine which allows the computer to calculate how much fuel is needed as well as some other things. You can buy CRC MAF Sensor cleaner spray and clean it off. Just be careful not to touch the sensor surface.

Changing the spark plugs is not much different than what you had to do when you were in your teens. They recommend changing the plugs every 100K. You will need a 5/8" plug socket and an extension. For the #8 plug (rear passenger side) it is helpful to use a 3/4" socket on the hex portion of the 5/8" plug socket. This gets you out past the exhaust manifold but not into all the A/C stuff. I always start with that one as the rest are much easier to get to. I would go with NGK or AC Delco plugs and change the plug wires as well. When you go to put the new plugs in, put a small dab of anti-sieze on the threads of the plug. Also, put some dielectric grease on the plug and coil ends of the plug wires. For the plug end, I like to take an old plug and put a dab of grease on the tip and shove it into the new plug wire. This get a good coating of grease in the connector.

 

[OR VietVet]

Besides the mileage effecting the sensors and cleaning the MAF and age of plugs, all of these are normal maintenance, I think it does have to do with the use of the wrong fuel. My recently new to me FatBoy set a code when I ran non ethanol fuel in it and when I changed to mt regular mid range fuel, like I run in my Tahoe, the code went away and has not been back. I would always err to the side of take care of old needed maintenance items but also watch out what fuel you are running.

 

[TNJYOUNG]

The MAF is the Mass Air Flow sensor. It is located just outside your airfilter housing in the intake tube. It measures the amount of air coming into your engine which allows the computer to calculate how much fuel is needed as well as some other things. You can buy CRC MAF Sensor cleaner spray and clean it off. Just be careful not to touch the sensor surface.

Changing the spark plugs is not much different than what you had to do when you were in your teens. They recommend changing the plugs every 100K. You will need a 5/8" plug socket and an extension. For the #8 plug (rear passenger side) it is helpful to use a 3/4" socket on the hex portion of the 5/8" plug socket. This gets you out past the exhaust manifold but not into all the A/C stuff. I always start with that one as the rest are much easier to get to. I would go with NGK or AC Delco plugs and change the plug wires as well. When you go to put the new plugs in, put a small dab of anti-sieze on the threads of the plug. Also, put some dielectric grease on the plug and coil ends of the plug wires. For the plug end, I like to take an old plug and put a dab of grease on the tip and shove it into the new plug wire. This get a good coating of grease in the connector.

Excellent advice! I am meeting a friend for lunch and will stop by the auto parts store on the way home. Hopefully they have the extension, plug socket, dielectric grease, and anti-sieze. This should be a fun afternoon project on these rainy days here ( I took the week off and the weather is crap).

 

[TNJYOUNG]

But if its a 13 and the gas cap is yellow its flex fuelView attachment 247884

I just checked and I do, in fact, have the yellow gas cap.

 

[Fless]

No matter the color of the gas cap (they can be changed) the inside of the gas filler door should indicate whether it's Flex or not. And do we know if any of this gas is E85? Or it it just the octane difference of the E10?

I have read that alternating E85 fillups with E10 fillups is not necessarily recommended; when changing from running E10 to E85, mixing the E85 in with half a tank of E10 can give the ECM time to adjust to the higher ethanol percentage. It may be best to stick with one fuel ethanol content.

While some of these educated assumptions about what code is setting the CEL may be correct, we don't really know what particular code is being set. All of the above-mentioned actions are typically regular maintenance items, and may have nothing or everything to do with the CEL.

 

[PG01]

No matter the color of the gas cap (they can be changed) the inside of the gas filler door should indicate whether it's Flex or not. And do we know if any of this gas is E85? Or it it just the octane difference of the E10?

I have read that alternating E85 fillups with E10 fillups is not necessarily recommended; when changing from running E10 to E85, mixing the E85 in with half a tank of E10 can give the ECM time to adjust to the higher ethanol percentage. It may be best to stick with one fuel ethanol content.

While some of these educated assumptions about what code is setting the CEL may be correct, we don't really know what particular code is being set. All of the above-mentioned actions are typically regular maintenance items, and may have nothing or everything to do with the CEL.

No sticker on my 13

 

[Fless]

No sticker on my 13

Which engine do you have, RPO code?