Checklist for electrical and CAN bus troubleshooting
Systematic inspection of electrical and electronic faults
Use the list as a fixed sequence when troubleshooting a vehicle's electrical system or electronic control units. Never skip the steps even if the fault seems obvious — many electrical faults have multiple interacting causes.
§Before you start
- 01Note the reported fault and under what conditions it occurs (cold, vibration, load).
- 02Connect a diagnostic scanner to the vehicle's diagnostic port and read all active and stored error codes.
- 03Note which control units do not respond to the CAN bus if any.
§Power supply and frame
- 01Check battery condition, voltage and terminals for corrosion.
- 02Check main fuses and relays for the affected circuit.
- 03Check ground connections for corrosion and loose connections.
§Cabling and connectors
- 01Check cables for damage, wear and moisture in connectors.
- 02Check connectors for corrosion, especially in exposed places like trailer coupling.
- 03Move cables and connectors during testing to reveal intermittent breaks.
§The bus and control units
- 01Confirm that all control units on the CAN bus respond correctly via diagnostic equipment.
- 02Kontrollér termineringsmodstande, hvis flere styreenheder mangler at svare samtidig.
- 03Delete error codes, repeat the test and confirm whether the error is reproducible or gone.
§Conclusion
- 01Document found errors, work performed and any component replacement.
- 02Perform a test drive where the original fault situation is recreated if possible.
- 03Inform the customer of observations that should be followed up later.