Diagnostic Test

CHARGING SYSTEM INSPECTION
NOTE:
This procedure is a general check of the entire charging system as a whole. It is designed to check all phases of a malfunctioning charging system that has no faults codes or in some cases, multiple fault codes.
1. Inspect the Battery terminals and cable ends for poor connection or corrosion.
2. Test the Battery with the Midtronics Battery Tester or equivalent for a shorted or dead cell.
3. Inspect the Alternator drive belt and tensioner for proper alignment and adjustment.
4. Inspect the vehicle for aftermarket accessories that may exceed the Alternator system output.
5. Inspect the fusible link in the charge wire or fuses in the PDC depending on application. If an open fusible link or fuse is found, use the wire diagram/schematic as a guide and inspect the wiring and connectors for damage.
  Were any problems found?
  
  Yes
  - Perform the appropriate repair.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 2
CHECK FOR HIGH RESISTANCE IN THE BATTERY GROUND CABLE
1. Perform a voltage drop test on the Battery Negative (-) cable from the Battery cable end;
  - to the engine ground eyelet.
  - to the body ground eyelet.
  Is the voltage reading above 0.2 volts for either measurement?
  
  Yes
  - Repair the Battery ground circuit for high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 3
CHECK THE PCM POWER AND GROUND CIRCUITS
1. Perform the CHECKING THE PCM POWER AND GROUND CIRCUITS test procedures. Refer to CHECKING THE PCM POWER AND GROUND CIRCUITS .
  Were any problems found?
  
  Yes
  - Repair the PCM power and ground circuit(s) as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
CHECK THE ALTERNATOR OUTPUT AT THE ALTERNATOR OUTPUT STUD
NOTE:
Make sure all testing equipment and cables are clear of any engine parts before starting the engine.
1. Start the engine.
  WARNING:
  When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
2. Hold the engine speed above 1157 rpm.
3. With the scan tool, navigate to data display and monitor the target charging voltage.
4. Using a voltmeter, measure the voltage between ground and the Alternator Output Stud.
  Is the Alternator overcharging or undercharging as compared to the target voltage?
  
  Alternator is overcharging
  - Go To 5
  Alternator is undercharging
  - Go To 12
CHECK THE PCM FUSED B+ VOLTAGE
1. With the scan tool, monitor the Battery voltage reading to the PCM.
2. Compare the reading to the voltage at the Alternator Output Stud.
  Is the voltage at the Alternator Output Stud equal to or above the Battery voltage reading on the scan tool?
  
  Above
  - Go To 6
  Equal
  - Go To 8
CHECK FOR HIGH RESISTANCE IN THE BATTERY POSITIVE CIRCUIT
1. Perform a voltage drop test between the Battery Positive (+) Post;
  - and the Alternator Output Stud.
  - and the PDC B+ terminal.
  Is the voltage reading above 0.2 volts for either measurement?
  
  Yes
  - Repair the Battery Positive (+) circuit for high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 7
CHECK THE FUSED B+ CIRCUIT FOR HIGH RESISTANCE
1. Turn the ignition off.
  CAUTION:
  Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.
2. Disconnect the PCM C1 harness connector and connect the (special tool #10436, Adapter, GPEC Diagnostic) in-line with the PCM C1 harness connector.
3. Start the engine and allow it to idle.
4. Measure the voltage between ground and the Fused B+ circuit at the GPEC Adaptor.
  Does the voltage read equal to the Battery voltage reading on the scan tool or equal to the voltage reading at the Alternator Output Stud?
  
  Voltage is equal to scan tool reading
  - Repair the Fused B+ circuit for high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  Voltage is equal to the Alternator Output Stud
  - Replace and program the Powertrain Control Module in accordance with the Service Information.
    Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE ALTERNATOR DUTY CYCLE
1. With the scan tool, check the Duty Cycle reading for the Alternator.
  NOTE:
  During normal operation the typical duty cycle of the field control at idle with minimal loads is approximately 35-40%, which will equate to between 4.0 and 5.0 volts. Depending on the charging issue, the PCM can drive the duty cycle to off (0%), which will equate to zero volts, or full field (100%), which will equate to between 11.0 and 12.0 volts.
  
  What is the Alternator duty cycle on the scan tool?
  
  0%
  - Go To 9
  100%
  - Go To 10
CHECK THE (K20) ALTERNATOR FIELD CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Back probe the (K20) Alternator Field Control circuit at the Alternator harness connector.
  WARNING:
  When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
2. Measure the voltage between ground and the (K20) Alternator Field Control circuit at the Alternator harness connector.
  Is there any voltage present?
  
  Yes
  - Repair the (K20) Alternator Field Control circuit for a short to voltage.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Verify that there is good pin to terminal contact in the Alternator and Powertrain Control Module connectors. If no problems are found, replace the Alternator. Refer to GENERATOR, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (A804) ALTERNATOR SENSE CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Alternator harness connector.
3. Disconnect the PCM C2 harness connector.
  CAUTION:
  Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.
4. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
5. Measure the resistance of the (A804) Alternator Sense circuit between the Alternator harness connector and the GPEC Adaptor.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 11
  No
  - Repair the (A804) Alternator Sense circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (A804) ALTERNATOR SENSE CIRCUIT FOR A SHORT TO GROUND
1. Check for continuity between ground and the (A804) Alternator Sense circuit at the Alternator harness connector.
  Is there continuity between ground and the (A804) Alternator Sense circuit?
  
  Yes
  - Repair the (A804) Alternator Sense circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Replace and program the Powertrain Control Module (PCM) in accordance with the service information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE DUTY CYCLE REQUESTED BY THE PCM
NOTE:
Before condemning an Alternator or PCM for a charging issue, it is important check the Battery Temperature Sensor reading. A Battery Temperature Sensor that is reading too high or too low can cause an undercharge or overcharge issue.
1. With the scan tool, check the Duty Cycle reading for the Alternator.
  NOTE:
  During normal operation the typical duty cycle of the field control at idle with minimal loads is approximately 35-40%, which will equate to between 4.0 and 5.0 volts. Depending on the charging issue, the PCM can drive the duty cycle to off (0%), which will equate to zero volts, or full field (100%), which will equate to between 11.0 and 12.0 volts.
  
  What is the Alternator duty cycle on the scan tool?
  
  0%
  - Go To 13
  Duty cycle is reading between normal and 100%
  - Go To 15
CHECK THE (A804) ALTERNATOR SENSE CIRCUIT VOLTAGE
1. Back probe and measure the voltage between ground and the (A804) Alternator Sense circuit at the Alternator harness connector.
  NOTE:
  With the Alternator connector plugged in, the voltage reading on the Alternator Sense circuit should be approximately 3.5 volts less that the voltage at the Alternator Output Stud due to the resistor inside the Alternator.
  
  Is the voltage reading for the (A804) Alternator Sense circuit equal to the voltage reading at the Alternator Output Stud?
  
  Yes
  - Go To 14
  No
  - Repair the (A804) Alternator Sense circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (A804) ALTERNATOR SENSE CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Alternator harness connector.
3. Measure the voltage between ground and the (A804) Alternator Sense circuit at the Alternator harness connector.
  Is the voltage reading for the (A804) Alternator Sense circuit equal to the voltage reading at the Alternator Output Stud?
  
  Yes
  - Repair the (A804) Alternator Sense circuit for a short to voltage.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Replace the Alternator in accordance with the Service Information.
    Refer to GENERATOR, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK DUTY CYCLE VOLTAGE AT THE ALTERNATOR
1. Back probe the (K20) Alternator Field Control circuit at the Alternator harness connector.
2. Measure the voltage between ground and the (K20) Alternator Field Control circuit at the Alternator harness connector.
  NOTE:
  Duty cycle of the field control at idle with minimal loads is approximately 35-40%, which will equate to between 4.0 and 5.0 volts, off (0%) will equate to zero volts, and full field (100%) will equate to between 11.0 and 12.0 volts.
  
  Does the voltage reading match up with the Alternator duty cycle on the scan tool?
  
  Yes
  - Replace the Alternator in accordance with the Service Information.
    Refer to GENERATOR, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 16
CHECK THE (K20) ALTERNATOR FIELD CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Alternator harness connector.
3. Disconnect the PCM C2 harness connector.
  CAUTION:
  Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.
4. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
5. Measure the resistance on the (K20) Alternator Field Control circuit between the Alternator harness connector and the GPEC Adaptor.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 17
  No
  - Repair the (K20) Alternator Field Control circuit for an open or high resistance. Make sure to check for a spread terminal at the PCM harness connector.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (K20) ALTERNATOR FIELD CONTROL CIRCUIT FOR A SHORT TO GROUND
1. Check for continuity between ground and the (K20) Alternator Field Control circuit at the GPEC Adaptor.
  Is there continuity between ground and the (K20) Alternator Field Control circuit?
  
  Yes
  - Repair the (K20) Alternator Field Control circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 18
CHECK RELATED PCM AND COMPONENT CONNECTIONS
1. Perform any Service Bulletins that apply.
2. Disconnect all PCM harness connectors.
3. Disconnect all related in-line harness connections (if equipped).
4. Disconnect the related component harness connectors.
5. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
  - Proper connector installation.
  - Damaged connector locks.
  - Corrosion.
  - Other signs of water intrusion.
  - Weather seal damage (if equipped).
  - Bent terminals.
  - Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  - Terminals that have been pushed back into the connector cavity.
  - Check for spread terminals and verify proper terminal tension.
  Repair any conditions that are found.
6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
9. With the scan tool, erase DTCs.
10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
11. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Replace and program the Powertrain Control Module (PCM) in accordance with the service information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  - Test complete.