Charging System: Testing and Inspection
Charging System Test
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
The engine control module (ECM) uses the generator turn ON control circuit to control the load of the generator on the engine. A high side driver in the ECM applies a duty cycled voltage to the voltage regulator. The duty cycle controls the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the generator turn ON control circuit. The ECM should detect low voltage on the generator turn on control circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect high voltage when the duty cycle voltage is commanded high and a low voltage when the duty cycle voltage is commanded low on the generator turn on control circuit.
The engine control module (ECM) uses the generator field duty cycle signal circuit, or F-terminal circuit, to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to high side of the field windings in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field windings on and off. The ECM uses the PWM signal input to determine the generator load on the engine. This allows the ECM to adjust the idle speed to compensate for high electrical loads. The ECM monitors the status of the generator field duty cycle signal circuit. When the ignition is ON and the engine is off, the ECM should detect a duty cycle near 0%. When the engine is running, the duty cycle should be between 5-99%.
Reference Information
Schematic Reference
Starting and Charging Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views [1][2]Alternator
Description and Operation
Charging System Description and Operation Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Circuit/System Verification
Note: Do not have a battery charger connected during the generator testing.
1. Ignition ON.
2. Verify that no G13 Generator or B18 Battery Current Sensor DTCs are set that would cause a charging system concern.
If DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
If no DTCs are set
3. Verify the scan tool Body Control Module Battery Voltage parameter is 12 V or greater.
If less than 12 V
Refer to Battery Inspection/Test Battery Inspection/Test.
If 12 V or greater
4. Engine running, all accessories OFF.
5. Verify the scan tool Body Control Module Battery Voltage parameter continually increases when controlling the Body Control Module Generator Regulator Setpoint from 10% to 80% with a scan tool. It may take up to 10 seconds for the battery voltage to stabilize between each setpoint change.
If the battery voltage does not continually increase
Refer to Circuit/System Testing.
If the battery voltage continually increases
6. All OK.
Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
1. Ignition OFF.
2. Test for less than 2 ohms between the G13 Generator housing and battery negative terminal.
If 2 ohms or greater
Repair the open/high resistance in the circuit.
If less than 2 ohms
3. Verify a test lamp illuminates between the G13 Generator B+ circuit terminal A X2 and ground.
If the test lamp does not illuminate and the circuit fuse is good
3.1 Remove the test lamp and disconnect the B+ cable at the G13 Generator.
3.2 Test for less than 2 ohms in the B+ circuit end to end.
If 2 ohms or greater, repair the open/high resistance in the circuit.
If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
If the test lamp does not illuminate and the circuit fuse is open
3.1 Remove the test lamp, disconnect the battery negative cable, and disconnect the G13 Generator B+ cable.
3.2 Test for infinite resistance between the B+ circuit and ground.
If less than infinite resistance, repair the short to ground on the circuit.
If infinite resistance, test or replace the G13 Generator.
If the test lamp illuminates
4. Test or replace the G13 Generator.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Generator Replacement Service and Repair