P1A8B SATURN - Volt Inverter Temperature High
- Restricted radiator air flow or coolant fans inoperative
- Restricted power electronics coolant flow or contaminated coolant
- Inoperative power electronics cooling system water pump
- Faulty Accessory Power Module (APM)
- Accessory Power Module (APM) harness is open or shorted
- Accessory Power Module (APM) circuit poor electrical connection
- Engine Light ON (or Service Engine Soon Warning Light)
P1a8b Saturn DescriptionThe Accessory Power Module (APM) controls the energy flowing 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. APM functions will run only when the APM Enable is active on the high speed hybrid GMLAN communication circuit.
Heat is generated in the 42-volt APM circuit solely through the demand for use of the EPS. The Engine Control Module (ECM) measures the temperature of the Power Electronics Cooling Loop and commands the flow of 2 electrical coolant pumps. The APM transfers heat in the 42-volt circuit to the APM Heat Plate which is then dissipated at the Power Electronics Front End Heat Exchanger.
Based on the severity of an overheat condition in the 42-volt circuit, the APM will make decisions ranging from notification of an over temperature condition to the EPS to completely shutting down the 42-volt power conversion.
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