What this code means
P0562 may mean a control module is seeing system voltage lower than expected.
What the vehicle may do
- A warning message or indicator may be displayed.
- A control module may be disabled.
- The concern may be current or may only show up intermittently.
Possible fault areas
- Possible battery condition concern
- Possible charging system concern
- Possible B+ feed circuit concern
- Possible ignition feed circuit concern
- Possible ground circuit open or high resistance
- Possible fuse or circuit protection concern
Diagnostic path
Opening: what P0562 is telling you
P0562 is a system voltage low code. In plain terms, a control module is seeing the vehicle voltage lower than it expects. On this Silverado 2500 diesel platform, that may show up as a warning message or indicator, and in some cases a module may be disabled. The broad fault areas are possible battery condition, charging system output, B+ feed circuits, ignition feed circuits, ground circuits, fuse issues, or, only after the circuit checks prove it out, the control module itself. For this code, the monitor is active with the ignition or vehicle on, and the low-voltage setting point is a B+ circuit less than 9 V for more than 5 s. This system-voltage diagnostic family also has a high-voltage side, where the B+ circuit is greater than 15 V for more than 5 s, but this episode stays focused on the low-voltage P0562 path.
Start with the basic checks
Before getting into connector testing, start with the basic system checks, follow a structured diagnostic approach, and make sure you understand how each diagnostic category is handled before you start. With the ignition on, look for system voltage codes in the control modules. If other system voltage faults are present, check what they mean first, because a low-voltage complaint may be vehicle-wide instead of isolated to one module. If that initial check does not point you elsewhere, shut the ignition off and make sure all vehicle systems are off before checking battery voltage.
Battery state before running tests
With the vehicle off and systems asleep, verify battery voltage at the C1 Battery. The expected range is 12.4 V to 12.8 V. If it is outside that range, stop and evaluate the battery before continuing. The battery voltage should stabilize after a few minutes with the ignition or vehicle off, so do not rush this check and chase a false reading.
Charging voltage and whether the fault is current
Next, start the engine with all accessories off and let the system voltage stabilize. At the C1 Battery, test for 13 V to 15 V. If the voltage is not in that range, move into charging system diagnosis before going deeper into module circuits. If it is in range, confirm whether the system voltage code is current. If it is not current, treat it as an intermittent condition. A non-current voltage fault can be related to an outside event, such as charging the battery or jump starting the vehicle, so keep that history in mind.
Set up circuit testing correctly
If P0562 is current after the battery and charging checks pass, move into circuit testing. Use the correct circuit information for the module you are testing so you identify the right B+, ignition, ground, and terminal locations. The modules do not all use the same circuit numbers, and the last two digits of the circuit number help identify the circuit function: primary fused B+, secondary fused feeds, ignition voltage, grounds, and low-reference grounds.
Ground circuit check
With the ignition or vehicle off, disconnect the connector at the appropriate control module. Check each ground circuit terminal with a test lamp to B+. The lamp should illuminate. If it does not, repair the open or high resistance in that ground circuit or ground connection. Also remember that some control module ground circuits may require up to 20 min after the ignition is turned off before achieving a resistance reading of less than 5 Ω. In most cases, the readings will drop below 20 Ω within 1 min as the modules go to sleep.
B+ feed checks
If the ground test passes, turn the ignition or vehicle on and check each B+ circuit terminal to ground with a test lamp. The lamp should illuminate. If it does not illuminate and the fuse is good, test that B+ circuit for an open or high resistance and repair the circuit fault if found. If no open or high resistance is found, verify the fuse is not open and that voltage is present at the fuse. If the fuse is open, test the B+ circuit for a short to ground. Repair the short if you find one. If that short is not found after the fuse-open path, the diagnostic path points to control module replacement. If the test lamp does illuminate on the B+ circuit, compare voltage at each B+ terminal to the C1 Battery. Each one should be within 1 V of C1 Battery voltage. If it is not, repair the high resistance on that B+ circuit.
Ignition feed checks
After the B+ feed checks pass, check each ignition circuit terminal to ground with a test lamp. The lamp should illuminate. If it does not and the fuse is good, test the ignition circuit for an open or high resistance and repair the circuit fault if found. If no open or high resistance is found, verify the fuse is not open and that voltage is present at the fuse. If the fuse is open, test the ignition circuit for a short to ground. Repair the short if you find one. If that short is not found after the fuse-open path, the diagnostic path points to control module replacement. If the ignition feed test lamp does illuminate, compare voltage at each ignition circuit terminal to the C1 Battery. Each one should be within 1 V of C1 Battery voltage. If it is not, repair the high resistance on the ignition circuit. If the ignition circuit voltage is correct after all the prior circuit checks, the diagnostic path points to control module replacement.
Verify the repair
Keep verification separate from the circuit testing. After the repair is completed, verify the repair and confirm the code stays gone. The code clears when the setting conditions are no longer present, and a history code will clear after 100 consecutive ignition cycles without a fault. The takeaway is simple: for P0562, prove battery state first, prove charging voltage next, then load-check the module grounds, B+ feeds, and ignition feeds before condemning a module. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0562 often needs a voltage-path diagnosis: battery state, charging output, module powers, ignition feeds, and grounds all may need to be proven before a module is blamed.
For more guided automotive diagnostics, visit STEP Diagnostics.
