Circuit Description
The purpose of the accessory power module (APM), integral to the starter/generator control module (SGCM), is to control the amount and direction of energy flowing between the 42v DC and 14v DC Buses via the APM, bi-directional 42v DC to 14v DC converter. During all of the APM functions the voltage is closely monitored between the internal voltage and the 12-volt underhood battery for voltage correlation faults.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0A8B 14-Volt Power Module System Voltage
Conditions for Running the DTC
| • | Engine is running for 30 seconds. |
| • | The SGCM has received voltage on the ignition 0 voltage circuit. |
| • | The SGCM has turned ON and no configuration DTC is present. |
| • | This diagnostic shall run every 100 milliseconds. |
Conditions for Setting the DTC
APM voltage is not equal to 12-volt battery voltage +/-2 volts.
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The driver information center (DIC), if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Electrical Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 |
Is the DTC set as current DTC? | -- | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections | ||||||
3 | With a scan tool, compare the 12-volt Converter Output Data from the SGCM data list, with the Desired Accessory Power data in the HPCM data list. Is the data parameter within the specified value? | +/-2 V | Go to Step 5 | Go to Step 4 | ||||||
4 | Test the battery positive circuit from the Underhood Fuse Block to the SGCM including the 175-amp fuse for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 5 | ||||||
5 | Inspect for poor connections at the harness connector of the SGCM. Refer to Testing for Intermittent Conditions and Poor Connections Connector Repairs . Did you find and correct the condition? | -- | Go to Step 7 | Go to Step 6 | ||||||
6 | Replace the SGCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 7 | -- | ||||||
7 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
