2014 Chevy Sonic 1.8 (non-turbo)
Codes: P0101 MAF Sensor Flow, P0171 Bank 1 Lean
Symptoms: Surging at idle, poor power, MIL (Malfunction Indicator Lamp) on
We had a fleet-owned 2014 Chevy Sonic 1.8 come into the shop the other day for an oil change and complaint of a MIL (Malfunction Indicator Light or check engine light), poor power, and surging at idle. I hooked up the Snap-On Verus Edge and found codes P0101 MAF Sensor Performance and P0171 Bank 1 Lean. Odd for a car with 45k on the clock that’s barely two years old, but I did a little digging and found a common problem with these little Daewoo-sourced engines: the intake boot from the air filter box to the intake manifold is very brittle and prone to tearing. A visual inspection confirmed my suspicions (photos below). The reason this was causing drivability problems was because the MAF (Mass Airflow Sensor) was located just upstream of this boot. This meant that “unmetered air” was entering the engine and confusing the computer. We called the dealer and they had the part on the shelf and made the comment that it was a very common problem. About 20 minutes later the customer was on the road with no more problems. Happy wrenching!