Diagnostic Routine B
Diagnostic Routine B
Diagnostic Overview
System Voltage Low or Battery is Discharged
Refer to Wiring Diagram Set 12 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
With the engine running, the charging system supplies voltage to the battery and the vehicle electrical system through the high current BJB (Battery Junction Box) and battery B+ cable. The PCM (Powertrain Control Module) monitors this B+ voltage through its own voltage supply circuit.
DTC (Diagnostic Trouble Code) Fault Trigger Conditions
Visual Inspection and Diagnostic Pre-checks
- Inspect for abnormal ignition-off current drain(s).
- Inspect the battery.
- Inspect high current BJB (Battery Junction Box) for loose or corroded connections.
- Inspect the generator clutch.
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. RETRIEVE PCM (Powertrain Control Module) DTCs (Diagnostic Trouble Codes)
1. Ignition ON.
2. Using a scan tool, perform PCM (Powertrain Control Module) self-test.
Is DTC (Diagnostic Trouble Code) P065B, U012D or U042E present?
2. CHECK BATTERY CONDITION
1. Ignition OFF.
2. REFER to Diagnostic Routine A: Battery Condition Test Pinpoint Tests to determine if the battery can hold a charge and is OK for use.
Does the battery pass the condition test?
3. CHECK THE GENERATOR CONNECTIONS
1. Disconnect and inspect all generator connectors.
2. 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
3. Reconnect the generator connectors. Make sure they seat and latch correctly.
4. Measure and record battery voltage.
5. Measure:
Is the voltage within 0.5 volt of the recorded battery voltage?
4. CHECK THE VOLTAGE DROP IN THE GENERATOR 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?
5. CHECK THE VOLTAGE DROP IN THE VEHICLE GROUNDS
1. With the engine still running at idle, headlamps on and heater blower on high, measure:
Is the voltage drop less than 0.5 volt?
6. MONITOR THE GENERATOR VOLTAGE DESIRED (GENVDSD) PID (Parameter Identification) WHILE COMMANDED
1. Using a scan tool, view the PCM (Powertrain Control Module) PIDs (Parameter Identifications).
2. Using the active command, set PID (Parameter Identification) GENVDSD to 14 volts.
3. Monitor the PCM (Powertrain Control Module) PID (Parameter Identification) GENVDSD.
4. With the engine still running at idle, measure battery voltage and record.
Is the recorded battery voltage within± 0.5 volt of the PID (Parameter Identification)?
7. COMPARE THE SUPPLY VOLTAGE (VPWR) PID (Parameter Identification) TO BATTERY VOLTAGE
1. With the engine still running at idle, headlamps on and blower on high, measure and record the battery voltage at the battery.
2. Using a scan tool, view the PCM (Powertrain Control Module) PIDs (Parameter Identifications).
3. Monitor the PCM (Powertrain Control Module) PID (Parameter Identification) VPWR.
Does the PID (Parameter Identification) accurately display battery voltage within± 0.5 volt of the recorded battery voltage?
8. CHECK PCM (Powertrain Control Module) GROUND FOR HIGH RESISTANCE
1. Monitor PCM (Powertrain Control Module) PID (Parameter Identification) VPWR.
2. With the engine still running at idle, turn off all accessory loads, measure the battery voltage at the battery and note the PCM (Powertrain Control Module) PID (Parameter Identification) VPWR.
3. With the engine still running at idle, turn headlamps on and blower on high, measure the battery voltage at the battery and monitor the PCM (Powertrain Control Module) PID (Parameter Identification) VPWR.
Does the PID (Parameter Identification) read within± 0.5 volt with accessory loads on as compared to accessory loads off?
9. MONITOR THE SUPPLY VOLTAGE (VPWR) PID (Parameter Identification)
1. With the engine still running at idle, turn off all accessory loads, measure and record the battery voltage at the battery and monitor the PCM (Powertrain Control Module) PID (Parameter Identification) VPWR.
2. Monitor the PID (Parameter Identification) VPWR and momentarily accelerate the engine to WOT (Wide Open Throttle) and release. Repeat this step 4-5 times while continuing to monitor the PID (Parameter Identification).
Does the PID (Parameter Identification) stay within 0.5 volt of the recorded battery voltage when the engine RPM (Revolutions Per Minute) are increased?
10. CHECK GENERATOR CLUTCH OPERATION
1. Ignition OFF.
2. Carry out the generator clutch component test. REFER to Generator Clutch Component Tests and General Diagnostics.
Is the generator clutch OK?
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) 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?
