For the year model, the TCM should have a LED light.
Flip up the passenger side carpet.
Turn ignition ON and note the blinking of the LED from the view window (round hole) on the ECM cover.
Count the blinking of the LED to get the code.
Under the shift lever there is only the interlock solenoid. Does it chatter only with the brake pedal depressed? The solenoid is not linked to TCM. Only to the brake switch and gear shift position.
Is the D4 and other indicators lights working correctly?
Erratic shifting could also be a fault with the TPS. Get it tested for smooth movement and correct voltage.
Wednesday, December 29th, 2010 AT 11:51 AM