Engine stalling in traffic accompanied by P0340 in your 2016 GMC Acadia creates both a driveability problem and safety concern. The camshaft position sensor code indicates the ECM is losing critical engine position data, which can cause stalling particularly at low RPM.
Understanding P0340
P0340 signals a malfunction in the camshaft position sensor circuit. The sensor monitors camshaft rotation, providing timing information for fuel injection sequencing and ignition. When this signal becomes intermittent or fails, the ECM can't properly control engine operation.
Why Stalling Occurs
At idle and low speed, the engine operates with minimal margin for timing errors. When camshaft position data becomes unreliable, the ECM's fuel and ignition timing calculations fail, causing rough running that can progress to stalling. Higher RPM may mask marginal sensor function.
Acadia Engine Considerations
The 2016 Acadia's 3.6L V6 has camshaft position sensors for each camshaft. P0340 typically refers to Bank 1, Sensor A, but similar codes exist for other sensors. Verifying which sensor is involved guides repair.
Stalling Danger
Stalling in traffic poses safety risks from loss of power steering assist and reduced brake boost. Diagnosing and repairing the cause promptly prevents potentially dangerous situations.