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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 33 (AUTOMATIC TRANSMISSION - ALLISON - DIAGNOSTICS (DTCs P0878-P2723)) >> DTC P0973 >> Circuit Description

Circuit Description

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Shift solenoid 1 (SS1) is a normally closed (N/C) solenoid that provides control main pressure to stroke shift valve 1. The transmission control module (TCM) determines the proper solenoid command logic to move shift valve 1 to attain a particular range.

The TCM provides voltage to pressure control solenoid 2 (PCS2) and shift solenoid 1, 2, and 3 (SS1, SS2, and SS3) through a separate solid-state device called high side driver 2 (HSD2). The TCM uses a low side driver to switch SS1 ON and OFF.

Since the valve state, stroked or unstroked, is critical to providing the correct transmission range, the shift valve has a pressure switch, located in the pressure switch manifold, to provide feedback to the TCM about the position of the valve.

DTC P0973 is a type A DTC.