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Home >> GMC >> 2008 >> Yukon Base, 5.3 J >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 4 (Hybrid Engine Control System) >> Diagnostic Information and Procedures >> DTC P1A89 >> Circuit/System Description
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Circuit/System Description

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The Accessory Power Module (APM) supplies the energy that flows between the high voltage, 300 volt, direct current (DC) and intermediate voltage, 42 volt, DC to support the Electric Power Steering (EPS). The APM receives a 42 volt enable command from the Hybrid Powertrain Control Module (HPCM) over the high speed hybrid GMLAN communication circuit. 42 volt APM functions will run only when the 42 volt APM enable is active on the high speed hybrid GMLAN communication circuit.