Check engine on road trip

[natetech]

Hi everyone,

During a road trip from high-altitude to low (home is Denver) last week, using the so-called 89 octane ethanol-added fuel in Nebraska, Iowa, and Wisconsin (fuel in Denver also has ethanol year round now... ugh)...

I romped on the accelerator in the '04 Yukon coming out of a rest stop in Iowa and the Check Engine light came on. It stayed on until mid-week in Wisconsin and went out.

Highway driving in Iowa on the return trip, it illuminated for a while again.

No signs of pinging, detonation, power loss (heck, it's getting so much O2 down there it felt like I had a new engine! GRIN!) etc.

Questions:

- Should I find a cheap code reader to read it soon?

- If I'm considering a tune, would it just be best to start with a more expensive reader/writer right off the bat? (Obviously if something's wrong it has to be fixed pre-tune.)

- Anyone ever seen similar behavior going from high-low altitude or vice-versa? Usual cause? Mass airflow sensor totally confused, etc!?

- Other thoughts?

I'll probably at least check what codes were set and post them. Truck is stock '04 GMC Yukon SLT with the mid-sized V8. Running fine and light is out back home a mile high.

Other info: Average Econ was 15 MPG for the whole trip. Normal?

Thanks!

 

[Thumper8302]

take it to autozone or other equivalent auto store and have the codes scanned for free.. could be somethin as simple as a gas cap.. but we wont know until u figure out what the code is... but yes i would figure out what it is real soon to try and help prevent anything major from leavin you stranded on the side of the road. ur mileage sounds around right.. let us know what u find out on the codes and we can go from there

 

[slowstang305]

Probably 02 sensor, autozone will read it for free

 

[natetech]

P0101 Mass Airflow Sensor - lots more air molecules down there. Made it cranky. No other codes.

Also have a K&N filter installed (came with the truck) so checked it. No problems.

Just more air than my Yukon is used to breathing, looks like.

 

[Thumper8302]

well if u have a k&n filter than u are more the likely gonna wanna clean that mass airflow sensor.... the thing with these filters they are oil charged..... therefor there is the high possibility that our mass airflow sensors wind up catching some of the oil from the filter..... When was the last time the filter was cleaned and recharged?

 

[natetech]

Cleaned and recharged about two months ago. Quite a while before the trip.

Checked after the trip and it's not in bad shape at all. Midwest is so wet there wasn't the usual dust. Mud in Wisconsin.

Killed the usual insane numbers of bugs on I-80 though!

Saw some other posts about cleaning the MAF and then some saying it was unnecessary. I guess I'll probably do it.

Truck's running fine, back home here in Denver.