Power dropped, errors across the whole truck
Updated: 2026-11-10
If the scanner throws a dozen codes from different systems at once, it is almost never ten separate faults — it is the power supply or the bus. A sagging voltage or a broken CAN twisted pair floods the whole truck with false codes.
How to approach it
Lost power means several units shut off at once, often from one cause: a broken earth, a short, or a blown main fuse. First check the battery terminals and the engine earth, then the main fuse and the relays. If some units work and others do not, trace the circuit that feeds the missing units. Power supply codes come as a group, so work through them in order.
The reference does not mark any code in this group as a reason to stop.
These codes usually come with it: SPN 158, SPN 168, SPN 627, SPN 628, SPN 629.
Other codes for this system
- SPN 158Battery Voltage At Ignition Switch
- SPN 168Battery voltage
- SPN 627Power Source
- SPN 628Program Memory
- SPN 629Controller #1
- SPN 3509Sensor Supply Voltage 1
- SPN 3511Sensor Supply Voltage 3
What happens if you keep driving
The electrical system is not holding voltage. While the engine runs the alternator carries it; shut it off and you may not restart.
Next the lights go, then modules start dropping out and false codes appear all over the truck. Get to somewhere with help without shutting the engine down.
That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.
What to check on the spot
Check the battery terminals and earth strap — corrosion and loose clamps throw false codes all over the truck. Running voltage should be 27–29 V.
Can I keep driving
The answer depends on the code, not the light. A yellow light is a warning; a red one means do not move. But even under a yellow light there are faults that require stopping right away — low oil pressure, overheating, lost brake pressure. Enter the code — the reference will tell you plainly whether to keep driving or stop.
Know the code number? Type it into the search — or paste the whole list from the scanner and we will show which fault is the real one.