P0562 - System Voltage Low
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the System Voltage Low (P0562). The signal is below the lower threshold, typically from a short to ground or an internally shorted sensor. The underlying code points specifically at the vehicle system voltage (charging system).
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| System Voltage Low – Permanent B+ Supply | Voltage (V) | 12.4 - 12.7 V (ignition OFF) / 13.5 - 14.7 V (engine running) | At module supply pins |
| System Voltage Low – Ignition-Switched Supply | Voltage (V) | 11.8 - 14.4 V | Ignition ON |
| System Voltage Low – Ground Connections Voltage Drop | Voltage (V) | < 0.1 V per ground point | Under load to battery negative |
| System Voltage Low – 5 V Reference Outputs | Voltage (V) | 4.95 - 5.05 V per circuit | Ignition ON, sensors unplugged one at a time |
At module supply pins
Ignition ON
Under load to battery negative
Ignition ON, sensors unplugged one at a time
Oscilloscope Waveform Analysis
500 ms/div, 5 V/divPossible Causes
A worn alternator, a poor main ground, or corroded battery terminals giving low or unstable charging voltage
Short to ground on the signal wire or an internal short circuit within System Voltage Low
Chafed or pinched wiring harness along the signal path to System Voltage Low
Poor ground connection or excessive voltage drop (> 0.1 V) at the ground point for System Voltage Low
Defective internal output driver or reference circuit in the control module for System Voltage Low
Symptoms
4
Recommended Solution
Measure battery voltage at idle and 2000 rpm with and without load (target 13.8–14.6 V); measure voltage drop on the alternator positive and ground cables (< 0.3 V).
Measure signal wire resistance to chassis ground with connector unplugged (must exceed 10 kΩ; low reading confirms short to ground).
Verify loaded supply voltage and harness terminal pins at System Voltage Low.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for System Voltage Low.
Inspect module enclosure and connector headers for water ingress, fretting corrosion, or PCB thermal damage.
Mechanic's Tip
Always test voltage drop in the charging cables before condemning the alternator — a corroded main ground sets the exact same code as a tired alternator.