4L60E Internal Wiring Harness with TCC Solenoid 1993-2002

This is the internal wiring harness for 1993-2002 GM 4L60E transmissions, sold as one assembly with the lock-up torque converter clutch (TCC) solenoid attached. It crosses to OE reference 350-0025. The harness runs from the round pass-through connector in the side of the case to the solenoids and pressure switch manifold on the valve body. Make sure your unit is a 1993-2002. The 2003-2006 harness (350-0061) is routed differently and uses a different TCC solenoid, so the two do not swap.

These harnesses live in hot fluid for years. The insulation gets hard and cracks, the wires rub through where they cross the valve body, and the pins in the case connector corrode or wick fluid. The TCC solenoid can also fail on its own. What you see: the converter will not lock up or drops out on the highway, the RPM runs high at cruise, TCC slip or TCC circuit codes such as P0740 or P0743, or shift solenoid circuit codes that come and go. Because the TCC solenoid comes on this harness, it makes sense to replace both at once instead of chasing one wire.

Before you buy, check the outside first. Unplug the case connector and look for fluid or green corrosion on the pins, and check the wiring from the connector back to the computer. If the outside is clean and the codes stay, go inside.

To swap it, drain and drop the pan and pull the filter. Unplug the harness from each solenoid and the pressure switch manifold. Remove the bolts that hold the TCC solenoid, press the tabs on the case connector, and push the connector into the case. Lay the new harness in the same path as the old one, keep the wires clear of moving parts, snap the connector back through the case, and bolt the TCC solenoid in. Put a new O-ring on the TCC solenoid and the case connector if they are worn, then install a new filter and pan gasket and refill.