GM Repair Problems? Ask GM Repair Expert Now.
Hi there, I am Cam. The timing is set by the ECM. Let me explain.Because of the computer controls, it does not use a standard advance system. Rather the computer changes the timing based on inputs from the crank sensor and the cam sensor. Because of this, and because there is no means to disable the timing like the older ones (1995 and older), a regular timing light cannot be used. Rather the timing is set by starting the engine, momentarily bringing the rpm over 1000 rpm then observe the CMP retard value. Ideally it is+/- 2º. Outside of that it will set code P1345.