8L45 Internal Wiring Harness 2015

This is a new GM internal transmission harness carrying reference number 24045609, listed here for the 8L45 and the 2015 model year. It is the piece that plugs into the round case connector on the side of the transmission and carries the solenoid, pressure switch and temperature sensor circuits inside the case. People shopping for it usually have a Camaro, Colorado, Canyon, ATS, CTS or CT6 that is setting solenoid circuit or fluid temperature sensor codes, a fluid leak at the case connector, or a harness that was damaged when the valve body came out.

What the internal harness does in an 8L45

The 8L45 is shifted entirely by the control module. It sends current to nine solenoids on the valve body: five clutch control solenoids, a line pressure solenoid, the TCC solenoid, the S8 default control solenoid and the S9 boost solenoid. The internal harness is the only path between the outside vehicle wiring and those solenoids, so a chafed wire, a loose terminal or oil wicking through the case connector can look exactly like a failed solenoid. GM now services this harness as two pieces: a pass-thru harness (item 37 in GM's illustration) that runs from the case connector, and a separate valve body harness (item 313). GM bulletin PIP5700G lists 24045609 as the pass-thru harness for vehicles without Start Stop. It also states that the old one-piece harnesses are no longer available.

Symptoms of a failing 8L45 internal harness

• Solenoid circuit codes for one or several solenoids, sometimes coming and going with temperature or bumps
• A P0711 fluid temperature sensor code, or temperature readings that jump around on a scan tool
• Failsafe operation stuck in one gear with the check engine light on
• Fluid weeping at the round case connector or oil inside the vehicle-side plug
• Harsh or erratic shifts that started right after valve body or harness work

How to confirm before you buy

Pull the codes and freeze-frame data first. Unplug the case connector and look for oil, green corrosion or pushed-back pins on both halves. Then check each solenoid circuit for resistance through the case connector and compare the readings with the valve body harness disconnected. If a solenoid reads correctly at its own terminals but wrong through the case connector, the harness is the problem. If the solenoid itself reads out of range, see our 8L90 and 8L45 shift solenoid guide instead. Shift quality complaints with clean electrical readings usually point to the valve body, covered in our 8L90 valve body testing guide.

Fitment

GM uses the same 24045609 pass-thru harness on 8L45 and 8L90 units without Start Stop (non-ESS), with either the 10-pin or the 4-pin internal mode switch. PIP5700G covers 2015-2017 Escalade and Yukon, 2015-2019 Corvette, 2015-2018 Silverado and Sierra 1500, 2016-2023 Camaro, 2016-2019 ATS and CTS, 2016-2018 CT6, 2017-2022 Colorado and Canyon, and 2017-2023 Express and Savana. The 8L45 itself first appears in that list in 2016 models, so the 2015 year in the title reflects the harness's first use in 8L90 vehicles. Two things to check: vehicles with Start Stop take a different pass-thru harness (GM 24298759), and the valve body harness must match your mode switch, 24046895 for the 10-pin style or 24046896 for the 4-pin style. Match the part number on your old harness, or send us your year and VIN. Every part for this family is on our 8L90 and 8L45 collection page.

Install notes

• The harness is replaced with the pan and filter off; on most units the valve body has to be lowered to route the new harness and clip it in place.
• Before you plug in the solenoids, identify S8 and S9 by wire color. Sonnax documents a 3-4 neutral caused by these two identical connectors being swapped: S8 default control has the green wire with blue tracer to terminal 1, S9 boost has the yellow wire with red tracer to terminal 7.
• Lube the case connector O-ring with ATF and seat it fully so it does not leak.
• Refill with DEXRON HP; GM lists a 7.4 quart service refill for the 8L45. Clear adaptives and run the shift learns after the repair.
• If a solenoid tested weak while you were in there, the 8L90 valve body solenoid kit or a single 8L45 TCC solenoid can go in at the same time.

Is GM 24045609 the complete internal harness?

GM lists 24045609 as the pass-thru harness that runs from the case connector. GM now services the internal harness in two pieces, and the valve body harness is a separate number (24046895 for a 10-pin mode switch, 24046896 for a 4-pin). Compare the photos and your old part before ordering.

Will this harness fit an 8L90?

Yes, if the vehicle does not have Start Stop. GM bulletin PIP5700G uses 24045609 for non-ESS 8L45 and 8L90 applications alike.

My truck has Start Stop. Is this the right part?

No. Vehicles with Start Stop use a different pass-thru harness, GM 24298759. Send your year and VIN if you are not sure which you have.

Can a bad harness cause a P0711 code?

Yes. The fluid temperature sensor signal runs through the internal harness, so a damaged wire or oil in the case connector can set P0711 or make the temperature reading erratic. Check the connector and harness before replacing the sensor.

I replaced the harness and now have no 3rd to 4th shift. Why?

Sonnax reports this is commonly caused by the S8 and S9 solenoid connectors being swapped. They are identical, so trace them by wire color: green with blue tracer goes to S8, yellow with red tracer goes to S9.

What fluid does the 8L45 use after the repair?

DEXRON HP. GM TechLink lists a 7.4 quart service refill for the 8L45.

• 8L90 Shift Solenoid Symptoms and Replacement
• 8L90 Valve Body Symptoms and Testing
• 8L90 Common Problems and Fixes
• 8L90 3-4 Clutch Failure: Symptoms and Fix