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Home >> Ford >> 2012 >> Mustang Base, 2D Coupe, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 144 (Four Wheel Drive (4WD) Systems -- F150) >> Diagnosis And Testing >> Four Wheel Drive (4WD) Systems - Electronic Shift >> Pinpoint Tests >> Pinpoint Test F: The Front Axle Makes Noise in 2H Mode Only and Generally Under Heavy Throttle >> Normal Operation

Normal Operation

WARNING: This page is about a different car, the 2012 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

In 2H mode, the TCCM provides a ground path to the IWE solenoid to supply vacuum to each IWE (disengaging the front hubs from the front axle). During certain conditions such as WOT maneuvers, manifold vacuum is lower than desired. To maintain uninterrupted IWE function in 2H mode, stored engine vacuum is sourced from the vacuum reservoir. A one-way check valve is implemented between the manifold and IWE solenoid/vacuum reservoir to prevent the stored vacuum from escaping into the manifold during low engine vacuum conditions. For noise-free IWE operation under all conditions, the check valve must be operating correctly.

This pinpoint test is intended to diagnose the following: 

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