Diagnostic Aids
A road test may be necessary to verify the customer complaint. If the "Scan" tester indicates TCC is turning on and off erratically, check the state of the 4th gear switch to be sure it is not changing state under a steady throttle position. If the switch is changing state, check connections and wire routing carefully. Also, if 4th gear switch is always open, the TCC may engage as soon as sufficient oil pressure is reached.