Generic
Type:
    Powertrain - Vehicle Speed, Idle Control, and Auxiliary Inputs - ISO/SAE Controlled
Description:
    System Voltage Unstable

GM
Type:
    Powertrain - Vehicle Speed, Idle Control, and Auxiliary Inputs - ISO/SAE Controlled
Description:
    System Voltage Unstable Conditions
Cause:
    Engine running, then the PCM detected a sudden change in the monitored system voltage that was more than 3 volts. Note: If DTC P1635 is also set, repair this trouble code first.