SureTrack Community Fix: Drunk Silverado

Today’s gasoline can contain varying amounts of alcohol, and flex fuel vehicles must monitor the fuel-alcohol content to run properly. SureTrack community member honkeykong had a 2009 Chevy Silverado in the shop for a idle and starting concerns and found the fuel-alcohol content reading higher than it should be. They posed the question to the community, and with the help of fellow community member JimA and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2013 Chevrolet Silverado 1500 LT 5.3L

Title
Rough idle, long start-ups, reset fuel-alcohol content.

Complaint
Customer complains that truck has rough idle and long start-ups. MIL is also on.

Diagnostic Steps Performed/Parts Replaced
Connected scan tool and found codes P0172 and P0175. Both banks rich. Long-term fuel trim (LTFT) both maxed negative. Could not locate any vacuum leaks anywhere. Looked at engine data while running and saw the alcohol content of the fuel shows 80%. Had the owner (used car lot) run 2 full tanks of regular 87 fuel through it and return. The concern is still present and the alcohol content is now 79%. Could not find option for fuel alcohol content re-learn on my scan tool. Is this high alcohol content reading my issue? Shouldn’t it be reading 10% or less on regular fuel? Is there any way to manually re-learn the alcohol content?

Best Answer from Community Member JimA
Should be able to reset alcohol content and fuel trims with scan tool. You may have to look around to find it.

Cause
Incorrect alcohol content reading causing drivability issues.

Correction
Found fuel-alcohol content reset in scan tool. Reset and vehicle now operates properly.

Editor’s Note
When doing a Fuel Composition Reset on any vehicle, ensure that the manufacturer’s procedures are followed. Failure to follow the prescribed procedures can lead to more drivability issues.