Engine will not start
Updated: 2026-11-10
The starter cranks but the engine will not catch — that is one thing; the starter does not turn at all — that is another. Start with power and ground: a weak battery keeps the control units from waking up properly and floods the truck with false codes. Next check fuel delivery and the speed sensors — without their signal the control unit will not allow injection at all.
How to approach it
The engine will not start: either there is no power for the starter and the control unit, or no fuel, or the control unit gets no timing signal. First check the battery voltage and the terminals, then the fuel level and the filter. If the starter turns but the engine does not catch, look at the fuel-system and timing codes. If the control unit has logged a code that stops the engine from starting, read it before cranking again and again.
The reference does not mark any code in this group as a reason to stop.
These codes usually come with it: SPN 168, SPN 158, SPN 1041, SPN 1081, SPN 729.
Other codes for this system
- SPN 168Battery voltage
- SPN 158Battery Voltage At Ignition Switch
- SPN 1041Start Signal Indicator
- SPN 1081"Wait to Start" Lamp
- SPN 729Intake Air Heater Driver #1
- SPN 730Intake Air Heater Driver #2
- SPN 723Engine speed (auxiliary sensor)
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.