Diagnostic Test

CHECK FOR AN ACTIVE DTC
NOTE:
Inspect and test the Battery with the Midtronics Battery Tester or equivalent for a shorted or dead cell before continuing with this test.
1. Start the engine and allow it to idle.
  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. With the scan tool, read the target charging voltage.
3. Measure the voltage between ground and the Alternator output stud.
  Is the voltage more than 1.0 volt above the target charging voltage?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
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 3
  100%
  - Go To 4
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 OK, replace the Alternator. Refer to GENERATOR, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (A804) ALTERNATOR SENSE CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the Alternator harness connector.
3. Disconnect the PCM C2 harness connector.
4. 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
  - Go To 5
CHECK THE (A804) ALTERNATOR SENSE CIRCUIT FOR AN OPEN/HIGH RESISTANCE
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.
1. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
2. Measure the resistance of the (A804) Alternator Sense circuit between the Alternator harness connector and the GPEC Adaptor.
  Is the resistance below 2.0 Ohms?
  
  Yes
  - Go To 6
  No
  - Repair the (A804) Alternator Sense circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
POWERTRAIN CONTROL MODULE (PCM)
1. Perform the CHECKING THE PCM POWERS AND GROUNDS test procedure. Refer to the appropriate Diagnostic information .
2. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Alternator and the Powertrain Control Module (PCM).
3. Look for any chafed, pierced, pinched, or partially broken wires.
4. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors.
5. Perform any Service Bulletins that may apply.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - If the PCM powers and grounds test good, replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .