Circuit Description
The powertrain control module (PCM) continuously monitors the system voltage. The system voltage information is taken from the PCM ignition positive voltage circuit. A voltage below 8 volts or above 18 volts causes improper system operation 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. A scan tool may not display data if system voltage is above 18 volts. Because of this, use a DMM in order to monitor system voltage to verify if the fault is currently present. A high voltage condition may cause a stalling condition or other driveability concerns.
Conditions for Running the DTC
The engine run time is more than 10 seconds.
Conditions for Setting the DTC
| • | The PCM senses the system voltage is above 18 volts. |
| • | All of the conditions are present 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 a predetermined gear. |
| • | The torque converter clutch (TCC) operation is inhibited. |
| • | The instrument panel cluster (IPC) displays a message. |
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 connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
| • | Test the generator voltage sense circuit for high resistance or loose connections. These could cause an intermittent overcharging condition. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical. |
| • | Using Freeze Frame and Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as 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 number below refers to the step number 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 or P1639 are set, refer to DTC P1635 5 Volt Reference 1 Circuit or DTC P1639 5 Volt Reference 2 Circuit for further diagnosis. Is the battery voltage less than the specified value? | 18 V | Go to Diagnostic Aids | ||
3 | Repair the charging system. Refer to Diagnostic System Check - Engine Electrical in 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 |
