4L70E Internal Wiring Harness, new and ready to install. Fits the 4L70E. Ships fast from the USA.
A tired internal harness on a 2003-2006 GM four-speed is easy to misread as a failed solenoid or a valve body problem. If your Silverado, Sierra, Tahoe, Yukon, Avalanche or Express is setting several solenoid circuit codes at once, will not engage the converter clutch, or shifts fine cold and goes into limp mode hot, this harness is a likely fix. It is listed as interchange 350-0061 (also 77995B and 74425T), replaces GM 15320476, and ships with a factory-style lock-up solenoid already on the harness.
The 4L60E-family harness is the wiring loom inside the pan. It picks up every circuit at the case connector and distributes them to the 1-2 and 2-3 shift solenoids, the 3-2 control solenoid, the pressure control solenoid, the TCC solenoids and the pressure switch assembly. The control module drives those solenoids by switching current and, on the pressure control solenoid, by varying it. Because the module reads circuit faults electrically, a single broken wire or a corroded terminal can look like several failed parts at once. The TCC solenoid that comes on this harness is the on-off lock-up solenoid that lets converter apply oil through.
Start with a scan tool and freeze-frame data. Watch the pressure control solenoid commanded current against actual; ATRA's Gears Magazine notes the command runs around 0.9 to 1.1 amps at idle, and an actual reading that does not follow the command often means an open or high-resistance circuit. Our pressure control solenoid guide walks through that test. Then check the external harness and case connector for oil and green corrosion. With the pan down, measure each solenoid circuit from the case connector side. If the circuits test good and the shift problem stays, look at the hydraulics with our valve body testing guide before spending money on wiring.
This version is listed for 2003-2006 GM trucks and vans with the 4L60E and 4L65E, and the listing also names the 4L70E. Be careful there: the 2006-and-later 4L70E and late 4L65E have an input speed sensor mounted on the pump, and those units take the 2006-on internal harness instead. Sonnax also points out that GM changed pressure control solenoid connectors around 2003, with early and late solenoids using different pin layouts, so a 2002-and-earlier unit is a different setup again. Match your old harness to GM 15320476 or 350-0061, or send us the year and VIN. Browse every part for the family on the 4L70E parts page.
No transmission removal is needed. Drain and drop the pan, remove the filter, unplug each solenoid and the pressure switch connector, unbolt the TCC solenoid, and press the case connector out from the inside. Lay the new harness in using the old one as a pattern so no lead rests against a moving part. Install a new case connector O-ring, refill with Dexron VI (the current GM fluid for this family), and clear codes. Many owners replace the solenoids while the pan is open; a 4L70E solenoid kit covers that job, and a TCC PWM solenoid is worth having if lockup quality was rough.
| Fits | 4L70E |
| Part type | Internal Wiring Harness |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
It is listed for 2003-2006 4L60E and 4L65E applications and replaces GM 15320476. If your unit has a speed sensor bolted to the back of the pump, use the 2006-on harness instead.
Yes. A factory-style lock-up solenoid comes attached to the harness.
We do not recommend it. Early units use a different pressure control solenoid connector, so match the part number on your old harness first.
Several circuit codes at once, faults that change with heat or vibration, and bad resistance readings from the case connector point at the harness. One code on one circuit usually means one solenoid.
Use Dexron VI, which GM now specifies for this transmission family. Check the level hot after the job.
