Internal harness with the lock-up TCC solenoid for 1993-2002 GM 4L60E. Fixes TCC and shift solenoid circuit faults from cracked wires or a bad solenoid.
Early 4L60E trucks and cars are now well past twenty years old, and the wiring inside the pan has been soaking in hot fluid the whole time. On a 1993-2002 Silverado, Sierra, C/K pickup, Tahoe, Yukon, S10, Blazer, Sonoma, Camaro or Corvette, a converter that will not lock, a P0740 that keeps coming back, or shift codes that appear and vanish over a bumpy road often come from this harness rather than from the solenoids it feeds. This assembly replaces the complete 1993-2002 internal harness, crosses to 350-0025, and comes with the lock-up TCC solenoid already attached.
The round pass-through connector in the side of the case is the only electrical doorway into the transmission. From there this harness branches to the shift solenoids, the 3-2 control solenoid, the pressure control solenoid and the pressure switch manifold, and it carries the TCC solenoid that bolts to the pump side of the valve body. When the PCM grounds the TCC circuit, that solenoid exhausts or holds oil to let the converter clutch apply. A wire that has cracked through its insulation or a pin that has wicked fluid can drop the circuit open for a moment, which the driver feels as lockup cutting in and out and the PCM records as a TCC electrical code.
ATRA's resistance chart for the early case connector lists the TCC solenoid between pins E and T at 20-40 ohms, the same range as the 1-2 and 2-3 shift solenoids on pins E-A and E-B. Measure each circuit from outside with the connector unplugged, then move the transmission side of the connector while watching the meter. Readings that jump or go open point to the harness. Because pin E is the shared feed, a bad terminal on that one circuit can set a whole string of codes at once, which ATRA documented on these units. Our TCC solenoid and P0740 guide and the shift solenoid testing guide explain each test in more detail. If everything measures good and lockup still slips, worn valve body bores are the next suspect, not the harness.
This harness is for the 1993-2002 GM 4L60E only. For 2003 GM redesigned the harness routing, the TCC solenoid and the connections, and that version crosses to 350-0061; the two cannot be swapped in either direction. If your transmission is a 2003 or later, use the 2003-2006 internal harness with TCC solenoid instead. Units built near the 2002-2003 changeover or swapped between vehicles can be mixed, so compare the harness and TCC solenoid on your valve body with the photos, or send us your year and VIN to check. Everything else we carry for this unit is on the 4L60E parts page.
| Fits | GM 4L60E automatic transmission, 1993-2002 |
| Replaces | 350-0025 |
| Includes | Internal wiring harness with lock-up TCC solenoid |
| Wire | Copper conductors |
| Weight | 14 oz |
| Not for | 2003-2006 4L60E (uses 350-0061) |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. The 2003-up harness (350-0061) has different routing and a different TCC solenoid. This one is for 1993-2002 transmissions only.
Yes. The lock-up TCC solenoid comes attached to the harness, so you replace both in one step.
Yes. With the case connector unplugged, measure each solenoid circuit at the transmission side. The TCC circuit on the early connector should read roughly 20-40 ohms, and the reading should stay steady as you move the connector.
At minimum a filter and pan gasket. If the original solenoids are still in the transmission, many owners replace them at the same time since they share the same age and the pan is already off.
Use Dexron VI, which GM approves in place of the older Dexron grades these transmissions originally used.
