While vehicle is in foward driving motion on street or highway(20 - 70mph)out of no where, truck will have a quick second halt in its motion, as if someone pulled and released the emergency brake(see attach recording) all i feel is a sudden jerk which its intensity depends on traveling speed. it startles me every time! during this time, the speed gauge drop then resumes regular speed, check engine light appear but immediately turns off as does the words "park assist off" also displays then immediately goes away. these sporadic episode are becoming more frequent and could cause tragic accident. i have made several attempts to have issue dignosed but unfortunately does not generate codes, according to onstar. dealership was unable to duplicate the issue. however they recommended replacing throttle position sensor, brake lamp switch, spark plugs and wires, master cyl and brake booster, flushing and replacing brake fluid for possible solutions but it did not fix the problem. what i have notice the issue becomes more frequent when there is studden braking(stop and go traffic) followed by increased acceleration. in addition while sitting idle in park for about 10mins with a/c on, truck idles down like it is about to cut off(engine light comes on then immediately off) but doesn't . dealership was unable to duplicate that too. also after braking for stop light i sometimes feel several thumps as though i'm not putting enough pressure on brake peddle. no matter how much pressure i put on brakes the thumps still sporadically occur. sometime when this happens it is followed by the first issue i meantioned when driving is resumed (hault,engine light, park assist off warning).
Electronic accelerator,cuts in and out, and accelerates without warning. *tr