P0625
Diagnostic Routine D
Diagnostic Overview
P0625, P0626
Refer to Wiring Diagram Set 12 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
The PCM (Powertrain Control Module) monitors the generator output via the generator monitor (GENMON) circuit (generator field terminal circuit). If the PCM (Powertrain Control Module) cannot read the GENMON circuit due to an open or short to ground, when the engine speed is greater than approximately 2,000 RPM (Revolutions Per Minute), the generator defaults to a steady voltage of approximately 13.5 volts and the PCM (Powertrain Control Module) sends a request to the IPC (Instrument Panel Cluster) to illuminate the charging system warning indicator. A GENMON duty cycle of 3% or less indicates a short to ground fault is present and results in DTC (Diagnostic Trouble Code) P0625 setting in the PCM (Powertrain Control Module). A GENMON duty cycle of 98% or more indicates an open or short to voltage fault is present and results in DTC (Diagnostic Trouble Code) P0626 setting in the PCM (Powertrain Control Module).
DTC (Diagnostic Trouble Code) Fault Trigger Conditions
Visual Inspection and Diagnostic Pre-checks
- Inspect fusible links.
- Inspect for abnormal ignition-off current drain(s).
- Inspect the radial arm adapter.
- Inspect the battery.
- Inspect the wiring, terminals or connectors.
- Inspect for loose or corroded connections.
- Inspect high current BJB (Battery Junction Box) for loose or corroded connections.
Special Tool(s)
Pinpoint Test
NOTE: Make sure battery voltage is greater than 12.2 volts prior to and during this pinpoint test.
NOTE: Do not have a battery charger attached during vehicle testing.
1. CHECK THE BATTERY CONDITION
1. Carry out Battery Condition Test to determine if the battery can hold a charge and is OK for use. REFER to Diagnostic Routine A: Battery Condition Test Pinpoint Tests.
Does the battery pass the condition test?
2. CHECK THE GENERATOR CONNECTIONS
1. Ignition OFF.
2. Disconnect and inspect all generator connectors.
3. Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary
4. Connect the generator connectors. Make sure they seat, latch correctly and are tightened to specification. REFER to Torque Specifications .
5. Measure and record battery voltage at the battery.
6. Measure:
Is the voltage within 0.5 volt of recorded battery voltage?
3. CHECK THE VOLTAGE DROP IN THE B+ CIRCUIT
1. Start the engine.
2. With the engine running at idle, headlamps on and blower on high, measure:
3. Carry out a wiggle test of the generator wiring and connections while measuring voltage drop.
Is the voltage drop less than 0.5 volt?
4. "A" SENSE CIRCUIT LOAD TEST
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
NOTE: This step puts a load on the "A" sense circuit. If there are corroded or loose connections, loading the circuit may help show the fault. A 250-350 mA incandescent 12-volt test lamp is required for this step. This circuit will not be loaded properly using an LED (Light-emitting Diode)-style test lamp.
1. Ignition OFF.
2. Disconnect: Generator C102A.
3. Using a 12-volt test lamp, check for voltage:
Does the test lamp illuminate?
5. CHECK THE GENERATOR MONITOR CIRCUIT FOR A SHORT TO VOLTAGE
1. Disconnect: PCM (Powertrain Control Module) C175B (3.5L) or C1381B (2.0L).
2. Ignition ON.
3. Measure:
Is any voltage present?
6. CHECK THE GENERATOR MONITOR CIRCUIT FOR A SHORT TO GROUND
1. Ignition OFF.
2. Measure:
Is the resistance greater than 10,000 ohms?
7. CHECK THE GENERATOR MONITOR CIRCUIT FOR AN OPEN
1. 3.5L engine, measure:
2. 2.0L engine, measure:
Is the resistance less than 3 ohms?
8. CHECK THE GENERATOR B+ INTERNAL RESISTANCE
1. NOTE: Failure to disconnect the battery will result in false resistance readings.
Disconnect the battery. REFER to Battery Disconnect .
2. Disconnect: Generator C102B.
3. Measure:
Is the resistance greater than 25K ohms?
9. CHECK THE RESISTANCE OF THE VOLTAGE REGULATOR INTERNAL CIRCUITS TO GROUND
1. Measure:
Are the resistances greater than 10,000 ohms?
10. COMPARE THE GENERATOR MONITOR (GENMON) AND GENERATOR COMMAND (GENCMD) PIDs (Parameter Identifications)
1. Connect PCM (Powertrain Control Module) C175B (3.5L) or C1381B (2.0L).
2. Connect a fused jumper wire:
3. Start the engine.
4. Using a scan tool, view the PCM (Powertrain Control Module) PIDs (Parameter Identifications).
5. Using the active command, set the GENVDSD PID (Parameter Identification) to 14.0 volts.
6. Monitor the GENMON and GENCMD PIDs (Parameter Identifications) while carrying out a wiggle test on the generator wiring harness.
Do the PIDs (Parameter Identifications) read within 2% of each other?
11. CHECK FOR CORRECT PCM (Powertrain Control Module) OPERATION
1. Ignition OFF.
2. Disconnect and inspect all PCM (Powertrain Control Module) connectors.
3. Repair:
- corrosion (install new connector or terminals - clean module pins)
- damaged or bent pins - install new terminals/pins
- pushed-out pins - install new pins as necessary
4. Reconnect the PCM (Powertrain Control Module) and generator connectors. Make sure they seat and latch correctly.
5. Operate the system and determine if the concern is still present.
Is the concern still present?
