Powertrain Control Module (PCM) - NGC
P0562-BATTERY VOLTAGE LOW
Special Tools:
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
The Powertrain Control Module (PCM) continuously monitors the system voltage. The system voltage information is taken from the PCMs ignition feed circuits. Since voltages that are out of range could cause improper system operation and/or component damage, the PCM operates in a default mode if a PCM voltage DTC sets. If the system voltage is low the PCM raises the idle speed in order to increase the generator output. If the system voltage is high, the PCM disables outputs to protect the hardware.
- When Monitored:
The engine running. The engine speed greater than 1000 RPM.
- Set Condition:
Battery voltage is less than 6 Volts. One Trip Fault.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.
1. ACTIVE DIAGNOSTIC TROUBLE CODE (DTC)
NOTE: Make sure the Battery is in good condition. Using the Midtronics Battery Tester, test the Battery before continuing.
NOTE: Inspect the vehicle for after market accessories that may exceed the Generator System output.
NOTE: Make sure the generator drive belt is in good operating condition.
NOTE: Inspect the fuses in the IPM. If an open fuse is found, use the wire diagram/schematic as a guide, inspect the wiring and connectors for damage.
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With the scan tool, read DTCs.
NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
Is the DTC Active or Pending at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.
2. BATTERY
NOTE: Make sure the Battery is in good condition. Using the Midtronics Battery Tester or an equivalent Battery tester, test the Battery before continuing.
Does the Battery pass the load test for this specific application?
Yes
- Go To 3
No
- Replace the Battery. Battery - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
3. (A11) B+ CIRCUIT HIGH RESISTANCE
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.
NOTE: Make sure all wires are clear of the engine's moving parts.
1. Measure the voltage between the (A11) B+ Terminal at the Generator and the Battery + Post.
2. Start the engine.
Is the voltage above 0.4 of a Volt?
Yes
- Repair the excessive resistance in the (A11) B+ circuit between the Generator and Battery.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 4
4. GENERATOR CASE GROUND HIGH RESISTANCE
1. Ignition on, engine not running.
2. Start the engine.
3. Allow the engine to reach normal operating temperature.
NOTE: Make sure all wires are clear of the engine's moving parts.
4. Measure the voltage between the Generator case and Battery ground post.
Is the voltage above 0.1 of a Volt?
Yes
- Repair excessive resistance in the Generator Ground between the Generator Case and Battery ground side.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 5
5. GENERATOR OPERATION
1. Turn the ignition off.
2. Disconnect the Generator Field harness connector.
3. Using a 12-volt test light connected to ground, probe the (K20) Generator Field Control circuit in the Generator Field harness connector.
NOTE: Make sure the test light is probing the circuit before actuating the Relay or a DTC may set and not allow the actuation.
4. Ignition on, engine not running.
5. Using the scan tool, actuate the Gen Field Control circuit.
Does the test light illuminate brightly and flash on and off?
Yes
- Verify that there is good pin to terminal contact in the Generator and Powertrain Control Module connectors. If OK, replace the Generator. Generator - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 6
6. (K125) GENERATOR FIELD CONTROL CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the C2 PCM 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 PCM Pinout Box (8815A) to perform diagnosis.
3. Measure the resistance of the (K125) Gen Field Control circuit from the Generator harness connector to the appropriate terminal of the PCM Pinout Box.
Is the resistance below 5.0 Ohms?
Yes
- Go To 7
No
- Repair the open in the (K125) Gen Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
7. (K125) GENERATOR FIELD CONTROL CIRCUIT SHORTED TO GROUND
1. Measure the resistance between ground and the (K125) Gen Field Control circuit in the Generator Field harness connector.
Is the resistance below 100 Ohms?
Yes
- Repair the short to ground in the (K125) Gen Field Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 8
8. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Generator and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. 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.
4. Perform any Technical Service Bulletins that may apply.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace and program the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.