SPN 168 FMI 17 — Battery voltage low during crank
What it means: Battery voltage low during crank.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Load test
Don't risk it — look up listed providers near you and give them this SPN/FMI when you call.
Listed providers nearest Phoenix, AZ
Closest first. Tell them SPN 168 FMI 17 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 Phoenix, AZ · (623) 304-4187
- 0.0 mi away — based in Phoenix, AZ · (480) 458-7715
- 0.0 mi away — based in Phoenix, AZ · (480) 530-7347
Applies to: Bendix · Detroit · Navistar · Paccar · Wabco
What SPN 168 FMI 17 means
Battery voltage low during crank.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- Weak batteries
- Bad cables
- Alternator
- Bad cables/grounds
- Batteries
- Cables
First moves (roadside)
- Load test
- Cable voltage drop
- Alternator test
- Load test batteries and alternator
FAQ
Battery voltage low during crank.
Serious — Power derate likely — plan to stop soon.
The most common cause is: Weak batteries. Other possibilities include Bad cables; Alternator; Bad cables/grounds; Batteries; Cables.
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 SPN 168 FMI 17, or share the same subsystem.
- Battery / Charging Voltage — Low (SPN 168 FMI 18)
- ECU Power Supply — Intermittent / Erratic (SPN 627 FMI 2)
- Engine Controller (ECM) — Internal Fault (SPN 629 FMI 12)
- 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)
- Lost Communication with Fuel Injector Control Module (U0105)
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
- System Voltage High (P0563) · 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
Find a mechanic or related guides
General diagnostic guidance for heavy-duty diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack). Not a substitute for a scan-tool diagnosis on your specific truck.