Diagnostics basics
Can you read the trouble codes of a van or a truck with an OBD scanner?
Yes, but not in the same way. A light van reads like a car: the same 16-pin OBD port, 12 V and the same generic codes. A truck or a bus usually runs on 24 V, uses the SAE J1939 protocol and sometimes has a round 9-pin connector, so you need a tool that supports that voltage and that protocol and, if needed, an adapter cable.
Reviewed by Daniel Morales, founder of Reprorace SL, on
How is a van like a car?
Light vans follow the emissions diagnostics of the cars in their class: a 16-pin J1962 port under the dashboard, 12 V and generic codes such as P0420 or P2002. Any OBD-II/EOBD scanner reads their engine.
The differences are in how they are used: lots of city miles, diesels with a particulate filter and DEF (AdBlue) and frequent stops, which make faults in those systems more likely.
What changes on a truck or a bus?
The voltage: many commercial vehicles run on 24 V, and a tool built only for 12 V can be damaged. Check that yours explicitly supports 24 V.
The protocol: heavy vehicles are usually diagnosed with SAE J1939 over CAN, with their own fault messages (DM1 for active faults). And the connector: some have the 16-pin port and others a round 9-pin connector, which needs an adapter cable.
Which tool do I need?
For a van, a normal OBD-II/EOBD scanner. For a truck, one that lists 24 V and J1939 in its specifications, not just "works with all vehicles".
To read other control units (transmission, brakes, body) or run service functions, each make has its own diagnostics, and you usually need truck diagnostic equipment or software.
What if it is a fleet?
With several vehicles, it helps if the device stays in each one and the shop can read it remotely when a warning light comes on, instead of moving the vehicle just to find out what is wrong.
Before you decide, check which diagnostic ports your vehicles have and which voltage they run on.
General guidance only: every manufacturer and model has its own details. Always follow your vehicle's manual and, if in doubt, ask a workshop.
Related
Related trouble codes
- U0001High speed CAN communication bus: malfunction
- P20EESCR NOx catalyst (bank 1, catalyst 1): efficiency below threshold
- P2002Particulate filter (bank 1): efficiency below threshold
Related symptoms
- AdBlue warning light on: what it means and what to do
- Diesel particulate filter (DPF) warning light: what to do
Learn more
Frequently asked questions
Can I use a car scanner on a truck?
Only if it supports 24 V and the J1939 protocol. A 12 V scanner can be damaged by 24 V.
Where is the diagnostic port on a truck?
It is usually in the cab near the driver, but it depends on the manufacturer: check the owner's manual.
Are vans inspected with the same OBD check as cars?
Light vans generally follow the same emissions diagnostics rules as the cars in their class; each country sets its own procedure, such as the MOT in the UK.