There's three common things to look at. First, use your foot to hold up the brake pedal. If it stops unlocking, check the switch adjustment.
Glitches in the throttle position sensor can cause signal voltage changes that make the Engine Computer think you're going to decelerate or coast to a stop. Those conditions trigger unlocking with relocking occurring a couple of seconds later. Those voltage changes stay within the acceptable range of signal voltages so no diagnostic fault code will be set for the sensor. This seems to affect diesel engines more than gas engines. You won't catch these glitches on a voltmeter or scanner display because they occur too quickly. You can graph the signal voltage when the problem occurs with a scanner that has record capabilities. By playing it back slowly you might see the voltage change. This is one time when it might make more sense to just pop on a new sensor to see if it solves the problem.
The last thing to look at is if your transmission still uses a kick down cable between it and the throttle body. In the '90s they sometimes became sluggish and would not retract under return spring pressure. The common complaint is delayed up-shifts and down-shifts that occur too soon, but intermittent unlocking can occur too.
Jul 7, 2013 at 12:16 AM
