Internal wiring harness with lock-up TCC solenoid for GM 4L60E, 4L65E and 4L70E transmissions 2003-2006; cures shift and converter-lockup fault codes.
On a 2003-2006 Silverado, Sierra, Tahoe, Yukon, Suburban or Express van, a 4L60E that sets random solenoid codes, loses lockup on the highway, or drops into limp mode and then shifts fine after a restart very often has a wiring problem inside the pan rather than a bad solenoid. The Rostra 350-0061 is a complete replacement internal harness for the 2003-and-later style 4L60E, 4L65E and 4L70E, and it comes with the torque converter clutch solenoid already attached. It is US-built and carries the 350-0061 reference number that many rebuild kits and diagnostic charts call for.
Every electrical signal the PCM sends to the transmission passes through this harness. It starts at the pass-through connector in the case, then branches to the shift solenoids, the 3-2 solenoid, the pressure control solenoid, the TCC PWM solenoid and the pressure switch manifold on the valve body. The on/off TCC solenoid is built into the harness itself, which is why the two are sold together. The harness sits in hot fluid for its entire life, so the insulation hardens, the wires rub where they cross the valve body and case, and the push-on terminals lose grip. Rostra's version uses an anti-bleed TCC solenoid designed to hold converter clutch apply pressure rather than letting it leak off, which helps lockup stay consistent.
ATRA has documented a crimp failure in one shared solenoid power circuit that could set P0740, P0753, P0758, P0785 and P1860 together, a good example of why a multi-code 4L60E deserves a wiring check before anyone buys solenoids.
Unplug the case connector and measure each solenoid circuit from the outside, then wiggle the harness while watching the meter. A reading that jumps or opens up while you move the connector is a harness fault. Pull the pan and look for shiny rub marks on the wires, cracked insulation, and terminals that slide loosely onto their solenoids. Our TCC solenoid and P0740 guide covers testing the converter clutch circuit, and the 3-2 solenoid and P0785 guide explains why limp mode with several codes so often traces back to wiring.
The 350-0061 fits the 2003-2006 style GM 4L60E, 4L65E and 4L70E. It does not fit 1993-2002 units, which use a different harness and connector layout; for those trucks use the 1993-2002 internal harness with TCC solenoid (350-0025). GM made running changes in this family, so compare the connector shape and solenoid layout on your valve body to the photos, or send us your year and VIN and we will check it. More 4L60E electrical parts are on the 4L60E parts page.
Drain and drop the pan, then unplug the old harness from each solenoid and from the inside of the case connector. Unclip it from the valve body, noting how it was routed. Fit the new harness along the same path, seat each terminal fully on its solenoid until it clicks, and make sure no wire rests on a sharp valve body edge. Replace the case connector O-ring so it does not weep. This is the right time to change a worn pressure control solenoid, and if you have converter slip codes rather than electrical codes, add the TCC regulator and isolator valve kit. Install a new filter and pan gasket, refill with Dexron VI, clear codes and drive through several lockup cycles to verify.
| Part number | Rostra 350-0061 |
| Fitment | GM 4L60E, 4L65E, 4L70E (2003-2006) |
| Includes | Internal wiring harness plus lock-up (TCC) solenoid, anti-bleed design |
| OE reference | 350-0061 |
| Not interchangeable with | 1993-2002 harness (350-0025) |
| Country of origin | United States |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is the 2003-and-later style harness. 1993-2002 4L60E units need the 350-0025 harness, which has a different layout.
Yes. The on/off lock-up solenoid comes attached to the harness, and it is Rostra's anti-bleed design.
No. The PWM apply solenoid is a separate part that plugs into the harness. Replace it separately if it tests bad.
Yes. A chafed wire or loose terminal on a shared circuit can set several solenoid codes at once and put the transmission in limp mode until the key is cycled.
Dexron VI ATF. Top up with the engine running and check the level hot after the road test.
