Problem After TCM Install

[Reilly Family]

I replaced the TCU transmission valve body on my 2004 Nissan Armada. The shifting problem it was having is now corrected but now when it downshifts going through 30 and 10 mph, the engine does a light surge. The dealer said the TCM unit programming was set and cannot be erased or reprogrammed. Does anyone know how to fix this surging problem? I appreciate any insight you can offer.

[VStar650CL]

You could try having the ECM updated, the TCM may have a later firmware version than your original. It's normal for the idle RPM to hover and then drop when decelerating at low speed, practically everything Nissan does that. It's deliberate, the ECM backs off the last few degrees of throttle plate closure in order to prevent stalling or backfire on drop-throttle.