It’s me again!! 2011 2.2L automatic. 204000 miles. I had some electrical issues that we got fixed through this site with tightening the under hood fuse box. Everything was working great for several weeks then it suddenly started stalling as I was slowing down or sitting at a stop. By the time I got it home I had a boatload of codes. P0011, P0014, P0102, P0171, P0300, P1133, U0073, B0081-71, C0460-42. I did test the fuel pressure at the rail and it was off. So this weekend I changed fuel pump Mass Air Flow sensor and both Oxygen sensors. I drove a couple miles to the gas station with no issues and it quit as I stopped at the pump. Put 10 in gas, and then just barely kept it running enough to get it home. Now it pulls 4 codes. P0171, fuel system lean, P0300, engine misfire, C0561-71 EBCM SYTEM DISABLED, and C0460-42 steering position sensor calibration. I have not checked the fuel pressure since putting in the new pump. The car has had new plugs and coil packs within the last month along with the EVAP purge solenoid. Timing chain was done earlier this year. Scratching my head is an understatement!! Thank you for you time!!!

 

https://www.obd-codes.com/p0171

Look for an exhaust leak before the first O2 sensor, a cracked manifold or damaged flex pipe, maybe a blown out exhaust manifold gasket or flange gasket

 

Check the fuse box again. Make sure the fuses are good and fully seated. Most of those codes indicate "circuit" problems; that could be (in no special order) bad sensors, broken wire disconnected wire, bad fuse, bad connection in the fuse box. Make sure the MAF is plugged in securely.
The C0561 is actually a computer connection thing, leads me to look at the connectors on the ECM, look for pins bent or pushed back out. Any connector that might have been disconnected then reconnected.

 

I have left the car sitting on the back burner and have finally gotten back to it. I had a crank position sensor for a couple years ago that had broken the clip on the harness, I replaced the sensor and the end on the harness today and checked for any codes. There were none I believe due to a dead battery for a few months. I took the car for a drive and went about 10 miles before it stalled at a stop sign. No SEL but still had 2 codes when I got back home. P0172 and P0011. I searched this sight and found the stuff about the alcohol percentage and found it to be 80.5%. I have only used the base standard gas so I don’t know if this would be a thing or not. Any ideas to try next??

 

The alcohol content is calculated using the amount of O2. More likely P0172 comes from a air leak.

 

I just noticed that the original set of codes showed a lean p0171 and now it is showing a p0172 rich code.

 

Could be the flex pipe.

 

GM issued a TSB that talks about Flexfuel cars getting confused about ethanol content in the tank. If they know what causes it, they didn't say. It's rare, but I even found a case where a later Silverado did it.

So you're sure you didn't put E85 in it?

Any chance you left the engine running while you fueled?

Does the car make a lot of short trips?

Sample the fuel and check actual ethanol content anyway. There are cheap kits, or Google how to just use a graduated cylinder if you have one.

Or take a chance and just reset the stored ethanol content to zero. You need a high-end scanner. (I had the dealer do it.)

Check for fuel line leaks.

 

Wait until the CEL lights up then read the codes. Only current codes matter.

 

Thanks for all of the help guys, still having problems. Just got back onto this car due to a failed fuel pump on my daily and it being back ordered for 2 weeks. I have gone through everything suggested except taking the heat shield off of the exhaust manifold. Everything else seems good. I did find a possible vacuum leak on the hose running from the valve cover to the rubber 90 above the throttle body. Now I am having the P0011, P0014, and P0172 codes that are reoccurring every few cycles. Car runs decent till completely warmed up and then extremely rough idle and sometimes stalling at stops. Is there some more vacuum issues worth tracking down. I have replaced both cam solenoids a couple times. The ones in there now should have less than 500 miles on them