How-to demonstration on performing a relative compression test using a digital storage oscilloscope (DSO) This method of testing can quickly provide a diagnostic technician direction when performing research on a vehicle with a driveability complaint such as a misfire, DTC, or other engine performance deficiency. Are you interested in advancing your skills as a diagnostic technician? Consider joining where you can continuously sharpen your diagnostic proficiency. Join today Every new membership begins with a 7-day free trial, no credit card required. After the trial, membership is $ or $219/year.