Complete solenoid and internal wiring harness kit for 2004-up GM 4L80E and 4L85E: TCC, EPC, shift A and B, harness, filter and pan gasket.
High-mileage 4L80E trucks and vans tend to fail electrically in clusters. A 2004 or later Silverado or Sierra 2500/3500, or an Express or Savana work van, starts setting P0740 one week and P0753 the next, shifts firmly, refuses to lock the converter, and then drops into limp mode on a hot day. This kit replaces the whole electrical side under the pan at one time: internal harness 24200161, TCC solenoid 24210864, EPC solenoid 24248892, shift solenoids A 24230288 and B 24230289, plus a filter and pan gasket.
In the 4L80E, the control module never touches the hydraulics directly. It sends power, ground and pulse signals through one internal harness to four solenoids on the valve body. Shift solenoids A and B open and close in combination to move the shift valves. The EPC solenoid receives a varying current and turns it into the pressure signal that sets line pressure. The TCC solenoid is pulsed to engage the converter clutch. Because all four share that harness and the case pass-through connector, one tired wire or loose terminal can trip codes on several circuits at once, and those codes often have nothing to do with the solenoid they name.
Pull every stored code, not just the current one. If several solenoid circuits are listed, start at the shared parts: the external connector at the case, the pass-through plug and the internal harness. Measure each circuit at the case connector, then again at the solenoid with the pan off. A good solenoid that reads bad through the harness points to the harness. Do not stop there, though. Transmission Digest documented a 2007 Express 3500 that kept setting P0753 and P0758 after the transmission, harness and solenoids had all been replaced, so the truck-side wiring has to be checked too. Our shift solenoid A and B diagnosis guide walks through the tests, and Silverado 2500 shift problems covers the pickup side.
For GM 4L80E and 4L85E transmissions built in 2004 and later. The 1991-2003 units use a different harness and a different EPC solenoid, and those parts do not interchange with this kit. Before ordering, look at the EPC connector and the harness routing in your pan, or send us your year and VIN and we will confirm. If you have an earlier transmission, see the other kits on the 4L80E parts page.
With the truck level, drain and drop the pan, then remove the filter and make sure the old seal did not stay in the case. Unplug the harness at each solenoid and at the pass-through, unclip it, and remove the solenoids. Coat the new O-rings with clean ATF so they slide in without rolling. Install the harness on the factory path, clipped so it cannot rub on the filter or the pan, then plug each solenoid in until it clicks. Sonnax notes that one of the plastic retention tabs on the pass-through connector often breaks, which lets the connector get pushed into the pan, so look closely at those tabs. Install the new filter and gasket, torque the pan evenly, fill with Dexron VI, clear codes and road test through lock-up.
If the pan is coming off for a full reseal, the 4L80E overhaul gasket and seal kit adds every other seal. If the shifts also slip, the 4L80E master rebuild kit covers the clutches the electronics cannot fix.
| TCC solenoid | 24210864 |
| EPC / pressure control solenoid | 24248892 |
| Shift solenoids | 24230288 (A), 24230289 (B) |
| Internal harness | 24200161 |
| Also includes | Filter and pan gasket |
| Transmission | GM 4L80E / 4L85E, 2004 and later |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. It is built for 2004 and later 4L80E and 4L85E units. A 2003 transmission uses the earlier harness and EPC solenoid, which are different parts. Send us your year and VIN if you are unsure which you have.
Two codes on separate circuits usually point to something they share, like the internal harness or the case connector. This kit replaces the harness and all four solenoids together, which covers both possibilities in one pan drop.
Heat makes cracked harness insulation and loose terminals open or short. That is typical of an aging internal harness on high-mileage 4L80E trucks and vans.
The kit already includes the filter and pan gasket. Check the case pass-through connector tabs, and if you are resealing the transmission, add an overhaul gasket and seal kit.
Fill with Dexron VI. Check the level hot after the road test, because the deep pan and cooler lines hold fluid that takes a few miles to circulate.
