Circuit Description
The starter/generator control module SGCM unit is an electronic device that works in conjunction with the electrical subsystem to efficiently perform DC/DC and DC/AC electrical energy conversion and support vehicle functions. The primary mission of the SGCM unit is to:
| • | The auxiliary power outlets APO function will convert 36 volt DC bus power to 120 volts AC. If the value of APO mode is OFF, then the APO function will be disabled and the APO Converter/Inverter will not transfer or consume any power. |
| • | The APO output AC voltage will represent the AC voltage measured at the output of the APO inverter. This signal will have the following specifications: |
| • | Range 120 volts AC, +5%, -8%, @ 20A |
| • | Frequency 60 Hz +/- 0.25 Hz |
| • | Provide 120 volts AC @60Hz energy for on and off board electrical equipment. |
The following DTCs are for external 120 volt AC harness failures, excessive current loads or internal system failures within the SGCM.
| • | B139A Output voltage of the converter is too low to meet current APO mode. |
| • | B139B Value of APO current is less than 60 amps. |
| • | B139C Value of APO current is greater than 60 amps. |
| • | B139E APO commanded ON, but the converter remains OFF. |
| • | B139F APO commanded OFF, but the converter remains ON. |
| • | B140A Internal SGCM circuit to monitor the ground fault detection. |
| • | B140C APO is disabled due to improper DC bus input voltage or excessive internal temperatures. |
Conditions for Running the DTC
| • | Engine running for 30 seconds. |
| • | The SGCM has received voltage on the ignition 0 voltage circuit. |
| • | The SGCM has turned ON and no configuration DTC are present. |
| • | This diagnostic will be run every 1.12 ms. |
| • | Reference voltage is stable and accurate. |
Conditions for Setting the DTC
| • | B139A DC/AC converter input voltage low. |
| • | B139B DC/AC converter current sensor low. |
| • | B139C DC/AC converter current sensor high. |
| • | B139D DC/AC converter output 1 current sensor high. |
| • | B139E DC/AC converter stuck OFF. |
| • | B139F DC/AC converter stuck ON. |
| • | B140A DC/AC converter output 1 ground fault circuit performance. |
| • | B140B DC/AC converter output 1 ground fault detected. |
| • | B140C DC/AC converter performance. |
Action Taken When the DTC Sets
| • | The 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, 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 | Yes | No |
|---|---|---|---|
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Electrical Connector End Views | |||
1 | Was the Engine Electrical Diagnostic System Check performed? | 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 in Wiring Systems |
3 | Inspect for poor connections at the 120 volt, orange harness connector of the starter/generator control module SGCM and auxiliary power outlets (APO). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
4 | With a DMM test the circuits of the 120 volt, orange harness for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 |
Important: Always perform the setup procedure for the SGCM. Refer to Service Programming System (SPS) in Service Programing. Replace the SGCM. Refer to Generator Control Module Replacement in Engine Electrical. Did you complete the replacement? | Go to Step 6 | -- |
6 |
Does the DTC reset? | Go to Step 2 | System OK |
