4T40E Internal Wiring Harness

If your 2004-2010 Chevrolet Cobalt, Malibu, HHR, Pontiac G5/G6, Saturn Ion or Vue is throwing several transmission electrical codes at once, dropping into a fixed gear, or shifting fine one day and harshly the next, the problem is often not a solenoid at all. It is the wiring inside the pan. This is a new GM internal wiring harness, reference number 24229665, for the 4T40E and 4T45E four-speed transaxle.

What the internal harness does in a 4T40E

Everything the PCM uses to control a 4T40E or 4T45E lives on or near the valve body: the two shift solenoids, the torque converter clutch PWM solenoid, the pressure control solenoid and the switch and sensor circuits the computer reads back. The internal harness is the bridge between all of those parts and the single pass-through connector in the case. Each solenoid gets its own plug, and the harness is clipped and routed along the valve body so it stays clear of the pan and the moving parts.

Because it sits in hot fluid for its whole life and is unplugged every time a valve body or solenoid is serviced, the harness ages. Insulation goes brittle, locking tabs snap, terminals spread, and a wire that was pinched or stretched during a previous repair can break inside the insulation where you cannot see it.

Symptoms of a failing 4T40E internal harness

• Check engine light with more than one solenoid circuit code at the same time, such as P0753 or P0758 (shift solenoid A or B circuit) together with P0748 (pressure control solenoid circuit)
• Codes that come and go with temperature, or only set on a hot drive
• Sudden default to a single gear, usually with very firm engagements
• Converter clutch that will not apply, or cycles on and off at highway speed
• Harsh or soft shifts that change from one drive to the next
• A new solenoid that did not fix the code it was bought for

How to confirm the harness is the problem

Read the codes first, then measure. With the pan off, unplug each solenoid and check resistance at the solenoid itself, then check the same circuit from the case connector. A good solenoid with a bad reading through the harness points to the harness. Wiggle the wires while watching a meter, look for melted or cracked connector bodies, and check the case connector pins for fluid wicking or corrosion. Our 4T40E and 4T45E problems guide covers the solenoid and valve body faults that cause similar symptoms, so you can rule those out before you buy.

Fitment

GM catalogs 24229665 for 2004-2005 Chevrolet Cavalier and Pontiac Sunfire, 2004-2005 Saturn L300, 2004-2010 Chevrolet Malibu, 2005-2010 Chevrolet Cobalt and Pontiac G6, 2005-2007 Saturn Ion, 2005-2010 Saturn Vue, 2006-2011 Chevrolet HHR, 2007-2009 Pontiac G5 and 2007-2008 Saturn Aura, in each case only with the 4T40E or 4T45E automatic. The V6 versions of several of those cars used a different transmission and do not take this part. The list starts at 2004, which lines up with the move to the smaller pressure control solenoid in most GM 4T40E/4T45E units, so a 1995-2003 car should not assume this harness fits. Compare the plug count and layout to the harness in your pan, or send us your year and VIN and we will check it. Every 4T40E part we stock is on the 4T40E parts page.

Install notes

The harness changes with the pan off and the transmission in the car on most of these vehicles. Drain the fluid, remove the pan and filter, unplug each solenoid and switch, release the harness clips and push the case connector out from the inside. Transfer nothing from the old harness unless the new one is missing a part your old one had. Route the new harness exactly as the old one was routed, make sure every connector clicks home, and keep wires away from the pan rail so the pan does not pinch them when it is torqued.

Use a new filter and pan gasket; our 4T40E/4T45E filter and pan gasket kit is the matching service kit. If a solenoid tested out of range during diagnosis, replace it now while the pan is down; the 2007-2009 solenoid kit and the 2004-up pressure control solenoid are the common ones. Refill with Dexron VI, clear the codes, and road test until the transmission is fully warm to confirm the codes stay gone.

Will this harness fit my 2003 Cavalier or Sunfire?

GM lists 24229665 from the 2004 model year on for the Cavalier and Sunfire. Earlier cars used the larger style pressure control solenoid and may need a different harness, so compare connectors with your old harness or send us your VIN before ordering.

Does it fit the V6 Malibu, G6 or Aura?

Only if that car has a 4T40E or 4T45E. Most V6 versions of these cars used a different transmission. Check the transmission code on your build label or send us the VIN.

Can I replace the harness without removing the transmission?

On most of these cars, yes. The harness is reached by dropping the pan, then unplugging the solenoids and pushing the case connector out from inside. Plan on a new filter, a pan gasket and a refill of Dexron VI.

I replaced a shift solenoid and the code came back. Is the harness the cause?

It is a common cause. Measure the new solenoid on the bench, then measure the same circuit from the case connector. If the solenoid is good and the reading through the harness is open, high or intermittent, the harness is the fault.

What fluid does the 4T40E take after the repair?

Dexron VI automatic transmission fluid. Refill through the fill point, then check the level hot on level ground with the engine running.