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Home >> Lincoln >> 2018 >> MKZ Select, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 565 (Four-Wheel Drive Systems) >> Diagnosis And Testing >> Four Wheel Drive (4WD) Systems - 2-Speed Torque-On-Demand >> Pinpoint Tests >> Pinpoint Test T : The Front Axle Makes Noise In 2H Mode Only And Generally Under Heavy Throttle >> Notes

Pinpoint Test T : The Front Axle Makes Noise In 2H Mode Only And Generally Under Heavy Throttle: Notes

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

Refer to Four-Wheel Drive System , for schematic and connector information.

Normal Operation 

In 4X2 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 4X2, stored engine vacuum is sourced from the vacuum reservoir. A one-way check valve is implemented between the vacuum reservoir and the IWE solenoid 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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