2002 Chevy 1500 Doesn’t Shift Until I Let Off Gas

There’s a linkage between the transmission and your accelerator that allows you to step down a gear so that you can pass other vehicles. It is much like the neutral-start switch that keeps your 1500 from starting until your foot is on the brake. Indeed, you can feel the linkage between the neutral-start switch when you leave your foot on the brake and cycle the switch.

Getting back to the step-down gear, it is sensitive not only to the speed at which you are traveling but also the throttle position. And, there is a software element involved the makes the operation of the step-down seamless.

Normally, when you step-down a gear, the throttle position sensor (TPS) tells the engine control module the position of the throttle. If it is within the range that the ECM (engine control module) coniders allowable for step down, then the ECM looks for other telltales. Those telltales include the MAF (mass airflow sensor) and MAP (the Mass Atmospheric Pressure) sensor, as well as the timing sensor and sensors at each wheel. The primary determinant in whether the step-down occurs are the MAF, TPS and timing sensors. If all of these sensors agree that a step-down to the next gear and an increase in torque is warranted, then the vehicle drops a gear and speeds up.

Now, what I think is happening in your vehicle is that one or more of your sensors is out of alignment with the others. Quite likely, it’s the MAF or MAP or a combination of both, plus the TPS that are out of alignment. In your case, they are giving the ECM incorrect information. If you have to let off the accelerator to allow a reset, then it is likely your software either needs an update or maybe it should be a combined with a sensor update to ensure that this problem is solved.

The sensor swap should cost about $300 or so while the software update could cost about $250, so it is shouldn’t cost very much go update and fix this problem.