Four-wheel drive will not engage

Hi,

The IWE (Integrated Wheel End) system uses vacuum hubs that engage or disengage the front wheel hubs from the front half-shafts. When you say they both are turning, are you referring to the half shafts that go from the differential to the front hubs?

Here is how it works. When the four-wheel drive system is in 2H mode, the 4X4 control module (PCM) supplies a ground path to the IWE solenoid to apply vacuum to the integrated wheel ends (disengaging the front hubs from the front half-shafts). In 4WD mode, the 4X4 control module (PCM) does not supply the ground path to the IWE solenoid, vacuum is not applied to the integrated wheel ends and an internal spring keeps the front hubs engaged to the front half-shafts. So, we have a couple of things that can be causing this. The internal springs are not installed properly, weak, or broken. Or, the IWE solenoid is maintaining vacuum to the hubs, keeping them disengaged.

Here is what I want you to try. If you look below, I attached a pic showing where the IWE solenoid is located. Disconnect the vacuum supply and plug it. See if the 4wd kicks in with that disconnected.

Let me know.

Joe

See pic below.

That sounds like a vacuum issue. Have you checked for any leaks (even small ones)?

Joe

Hi,

It could indicate a few things, and yes, the solenoid itself could be bad. The interesting thing is this. When there is no vacuum, the front wheels should engage. If there is vacuum, it should stay in 2wd. Something is preventing the vacuum from releasing and engaging the front axles. The idea that it is both sides tends to lead me to believe the problem is before the hubs. At this point, I'm thinking it could be the module or the IWE solenoid.

As far as how it works, it is both electrical and vacuum actuated. When the four-wheel-drive system is in 2H mode, the 4X4 control module (PCM) supplies a ground path to the IWE solenoid to apply vacuum to the integrated wheel ends (disengaging the front hubs from the front half shafts). In 4WD mode, the 4X4 control module (PCM) does not supply the ground path to the IWE solenoid, vacuum is not applied to the integrated wheel ends and an internal spring keeps the front hubs engaged to the front half shafts.

With that in mind, something is preventing the vacuum from being removed from the hubs.

I hope that makes sense. Sorry it's so long. Just trying to explain.

See pic below. Check all wiring related.

Let me know what I can do to help.

Take care,

Joe

Dave, you are very welcome, and I totally understand. Not being there makes it difficult from my end. If possible, could you let me know what was causing the problem?

Joe

Hi, Dave.

Has anything been identified as the cause of the problem? I'm interested in knowing.

Joe

Wow, that is more than I expected. Do you plan to do any of the work yourself, or has it already been done?

Let me know if I can help. Also, thanks for the update.

Joe

Dave, you are very welcome. Please feel free to come back anytime.

Take good care of yourself,

Joe