Dear Doctor: I recently had a couple of no-start conditions on my 2002 GMC Envoy. In both cases I moved the gearshift handle from Park to Drive and then back to Park and then the SUV started. On Thanksgiving Day it happened again. Nothing I did would allow it to start. We called a tow to bring it to my mechanic and it started for the tow truck driver. I drove the car to my mechanic and left it with him for a few hours. The condition could not be duplicated and there were no codes in the computer. Can you help? I am afraid to drive anywhere. Cindy
Dear Cindy: Intermittent conditions, such as yours, are sometimes difficult to diagnose. The problem can be anything from the ignition switch, neutral safety switch, starter relay, or starter motor. At my shop we would hook up a test light bulb to the starter motor (S) terminal and position the light so the driver can see the light when starting the vehicle. This will show if there is voltage at the starter when the key is turned. This is where you have to start.