C601 - Driver airbag stage 1 firing circuit open airbag control unit fault

What does error code C601 mean in the airbag control unit?

Error code C601 reports, on Citroën vehicles, an interruption in the ignition circuit of the driver airbag, specifically in the first-stage driver airbag ignition module, in other words the component that fires the driver airbag. The airbag control unit stores this fault and switches on the airbag warning light, so the fault in the restraint system is displayed.

An interruption means that the electrical current path to the ignition module is not continuous. As long as this condition persists, the entry remains stored in the fault memory of the airbag control unit.

How do you recognise error code C601?

You can recognise error code C601 by the airbag warning light staying on permanently, as the code is stored in the fault memory and cannot be permanently cleared. It is read out with a diagnostic tool, which displays the entry in the airbag control unit's fault memory and thus identifies the affected ignition circuit of the driver airbag.

The airbag warning light stays on permanently for as long as the entry is in the fault memory. Clearing the code without rectifying the cause does not make it disappear for good.

The exact entry is read out with a diagnostic tool, which is why reading out the fault memory comes before any further checks.

What causes error code C601?

Error code C601 is caused by an interruption in the ignition circuit of the driver airbag, which may lie in a connector, a cable, the airbag module or the airbag control unit itself. Where exactly the fault lies is only shown by testing at a specialist workshop, as the error code alone does not name the faulty part.

• A loose, dirty or corroded connector in the driver airbag's ignition circuit
• Damaged or broken cables between the airbag control unit and the driver airbag
• A faulty driver airbag module with the first-stage ignition module
• Ageing electronic components, soldered joints, or moisture and corrosion in the airbag control unit itself

Which of these causes applies will be established by targeted measurements at a specialist workshop.

In which vehicles does error code C601 occur?

Error code C601 is known for Citroën vehicles, specifically the models Citroën C3 Aircross III, Citroën C3 Picasso I, Citroën C4 Aircross I, Citroën C4 Cactus I, Citroën C5 Aircross II and Citroën ë-C3 IV. On other vehicles the meaning of the code may differ, and the list of models does not claim to be complete.

All the models named are Citroën vehicles. Whether error code C601 occurs on a specific vehicle can only be established by reading out the fault memory with a diagnostic tool.

How is error code C601 resolved?

Error code C601 is resolved by first reading out the fault memory with a diagnostic tool and then having the connectors, cables and driver airbag module checked at a specialist workshop. If the cause lies in the airbag control unit itself, the unit is sent to Airbag24 for repair after removal.

As the code points to the ignition circuit, have the connectors, cables and driver airbag module checked at a specialist workshop first. Work on the airbag system should be carried out by qualified specialists.

Only once the connectors, cables and module have been found to show no fault does the airbag control unit come into question as the cause. For removal, you first disconnect the battery and only then remove the control unit. You then create a repair order online and send the unit in to Airbag24. Inspection, repair and testing usually take 3–4 working days.

The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.