P0563 — System Voltage High
What it means: System Voltage High.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Test alternator output at high idle
Don't risk it — look up listed providers near you and give them this code when you call.
Listed providers nearest Sparks, NV
Closest first. Tell them P0563 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Sparks, NV · (775) 355-6884
- 0.0 mi away — based in Sparks, NV · (775) 356-7200
- 0.0 mi away — based in Sparks, NV · (775) 359-0550
Seen on: Heavy Truck
What P0563 means
System Voltage High. Common causes: System voltage above 16V.
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
System Voltage High. Common causes: System voltage above 16V.
Serious — Power derate likely — plan to stop soon.
The most common cause is: System voltage above 16V. Other possibilities include Overcharging alternator; failed voltage regulator.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside P0563, or share the same subsystem.
- ECU Power Supply — Intermittent / Erratic (SPN 627 FMI 2)
- Battery / Charging Voltage — Low (SPN 168 FMI 18)
- Engine Controller (ECM) — Internal Fault (SPN 629 FMI 12)
- Battery voltage low during crank (SPN 168 FMI 17)
- J1939 proprietary datalink lost (SPN 625 FMI 9)
- J1939 Data Link — Communication Error (SPN 639 FMI 2)
- High Speed CAN Bus Fault (U0001)
- Lost Communication with ECM/PCM (U0100)
Same symptom: Charging and voltage
Other codes that trace back to voltage — one bad ground can set half a dozen of them at once.
- System Voltage Malfunction (P0560) · Electrical, Charging & Network
- System Voltage Low (P0562) · Electrical, Charging & Network
- Starter Relay Circuit High (P0619) · Electrical, Charging & Network
- Generator Control Circuit (P0620) · Electrical, Charging & Network
- Generator Field F Terminal Circuit (P0622) · Electrical, Charging & Network
- Generator Field Terminal Circuit Low (P0625) · Electrical, Charging & Network
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.