Next I would use a scanner to view live data and to read any diagnostic fault codes. A dirty spot on the throttle position sensor can make it appear to the computer as though you're headed for idle or wide-open-throttle, two conditions that will initiate a momentary converter unlock, but if the sensor fails completely, it will set a fault code. A simple glitch in the reading may not set a code but it can lead to the converter unlocking.
Most scanners have a record function that allows you to record a few seconds of data to be reviewed slowly, later. You press the button when the problem occurs, but since the data travels through the scanner's memory, the recording actually starts a couple of seconds before you pressed the button. That will allow you to see what happened when the event occurred. If it works like the Chrysler scanners, you can include switches in the list of recorded data. That means you can add the brake light switch to the list.
If you watch the throttle position sensor's signal voltage, it should remain steady when you hold the accelerator pedal steady. That works best if you have the cruise control on. You'll see very slow and small changes take place. The clue you're looking for is if it suddenly pops from, lets say, 2.86 volts to 3.22 volts, then back again. The throttle won't move that quickly with the cruise control.
Tuesday, August 1st, 2017 AT 10:22 AM