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P0563 — System Voltage High
SeriousElectricalPower derate likely — plan to stop soon
Seen on: Heavy Truck
System Voltage High. Common causes: System voltage above 16V.
Don't risk it — get a diesel tech on the truck.
Your code rides along, so nearby mechanics see the fault before they quote you.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- System voltage above 16V
- Overcharging alternator
- failed voltage regulator
First moves (roadside)
- Test alternator output at high idle
- replace regulator or alternator if over 14.8V
FAQ
What does P0563 mean?
System Voltage High. Common causes: System voltage above 16V.
How serious is P0563?
Serious — Power derate likely — plan to stop soon.
What's the most likely cause of P0563?
The most common cause is: System voltage above 16V. Other possibilities include Overcharging alternator; failed voltage regulator.
Can I keep driving with P0563?
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Throwing this code right now?
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.