A ticking or knocking sound may be heard on some 2016-2017 ATS, CT6, CTS, Camaro; 2017 LaCrosse, XT5, Colorado, Canyon and Acadia models equipped with the 3.6L engine (RPO LGX). The 3.6L engine uses Active Fuel Management (AFM) to conserve fuel. The ticking or knocking sound may be heard coming from the AFM cylinders. DTCs P0300 (Engine Misfire Detected), P0302 (Cylinder 2 Misfire Detected) or P0305 (Cylinder 5 Misfire Detected) may be set.
The ticking or knocking sound may be heard all the time, only under load, or intermittently. The sound may be caused by spongy stationary hydraulic lash adjusters (SHLA) (lifters) or a damaged switching roller finger followers (SRFF).
TIP:Prior to disassembly of any components, record a sound file or video with sound of the engine running. The file may be needed when contacting the Technical Assistance Center (TAC) or may be requested by GM Engineering.
Refer to #PIP5486 for diagnostic and repair instructions. The diagnostic steps must be performed in order.
诊断包括验证喷射器不会泄漏并导致由于一个气缸中的过量燃料而导致噪音以及检查进气阀杆和阀的顶部的过量碳。
If the sound is still evident after these steps, test for soft or spongy stationary hydraulic lash adjusters (SHLA). (Fig. 11)
Fig. 11
It also may be necessary to inspect the switching roller finger followers (SRFF) for any damage, such as a stuck locking pin or fractured torsion spring. (Fig. 12) If any one of the SRFFs are damaged, replace all four on the affected cylinder.
Fig. 12
– Thanks to Aron Wilson
