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Home >> Chevrolet >> 2018 >> Suburban 3500 HD LT >> Repair and Diagnosis >> External Pages >> Different car >> Section 9 (Engine Controls And Fuel - 5.3L (L83) Or 6.2L (L86) - DTC P0443 To DTC P3452 And Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> DTC P050D: Cold Start Rough Idle >> Circuit/System Description

Circuit/System Description

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For an overview of the component/system, refer to Fuel System Description

During a cold start, the engine control module (ECM) commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the fuel injectors are energized twice during each injection event. As with misfire diagnosis, in dual-pulse mode the ECM monitors the crankshaft position sensor and the camshaft position sensors to calculate crankshaft rotation speed. In normal operation, optimum fuel delivery during dual-pulse mode produces a steady crankshaft rotation speed. If the variations exceed a calibrated value, the DTC sets.