Circuit Description
The PCM continuously monitors the system voltage. The system voltage information is taken from the PCMs ignition feed circuits. Since voltages below 8.0 volts or above 17.1 volts, 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 most outputs to protect the hardware. Class 2 Serial Data is shut down when system voltage is below 9.2 volts or above 16.0 volts. A scan tool will not display data if system voltage is outside this range. Because of this, use a DVM in order to monitor system voltage when checking to see if the fault is currently present.
Conditions for Running the DTC
| • | Engine operates longer than 10 seconds |
| • | Engine speed is greater than 1000 RPM |
| • | Vehicle speed is greater than 8 km/h (5 mph) |
Conditions for Setting the DTC
The PCM senses system voltage above 17.1 volts for 5 seconds.
Action Taken When the DTC Sets
| • | The PCM stores DTC P0563 in the PCM memory when the diagnostic runs and fails. |
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | The PCM will record the operating conditions at the time the diagnostic fails. The PCM stores this information in Failure Records. |
| • | The PCM disables most outputs. |
| • | The transmission defaults to third gear. |
| • | TCC operation is inhibited. |
| • | During the time the fault is present, the PCM will cycle the fans ON and OFF every few seconds. |
Conditions for Clearing the DTC
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
Important: Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM\TAC modules.
| • | Check the generator voltage sense circuit for high resistance or loose connections. These could cause an intermittent overcharging condition. Refer to Charging/Starting for circuit details. |
| • | Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. |
For an intermittent, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Important: If DTC P1635 and/or P1639 are set, refer to those DTCs for further diagnosis. Is the battery voltage less than the specified value? | 17.1V | Go to Diagnostic Aids | ||
3 | Repair the Starting/Charging system. Refer to Engine/Engine Electrical Is the repair completed? | -- | -- | |
4 |
Does the scan tool indicate that this test ran and passed? | -- | ||
5 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
