C1602
ChassisManufacturer-Specific Chassis/ABS Fault
On Citroen, DS, and Peugeot models specifically, this code typically indicates a fault in the central control system, most commonly battery voltage or BSI (body system interface) communication. The exact meaning varies by model year and which BSI version the car has.
ⓘ Information only. This page provides general educational information about fault code C1602. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does C1602 mean?
C1602 is a Chassis (ABS, traction control, steering) fault code. It indicates: Manufacturer-Specific Chassis/ABS Fault.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Multiple warning lights illuminated on the dashboard at once
- • Various electrical systems behaving oddly: windows, central locking, lighting, climate control all sometimes affected
- • Engine warning light on
- • Sometimes hard or no starting
- • Battery drain when the car is parked, the BSI may not be going to sleep properly
- • On some models, dashboard displays going blank or rebooting
Possible causes
Causes commonly associated with C1602, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Weak or failing battery, the most common cause by a wide margin on French cars; the BSI is sensitive to voltage drops
- 2. Poor battery terminal connections, white or green corrosion on the posts
- 3. Failed BSI unit (the central body computer), known weak point on PSA group cars
- 4. Aftermarket electrical work, alarms, dashcams, or trackers spliced badly into the car's network
- 5. Damaged earth connections, a corroded earth strap is a frequent silent cause
- 6. Software bug on certain model years, dealer reflash sometimes needed
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Check battery voltage first, healthy is 12.6V engine off, 13.7-14.7V running. Below 12.4V is your prime suspect
- 2. Inspect battery terminals for corrosion, clean and reseat if there's any green/white deposit
- 3. Disconnect any aftermarket electronics added to the car (alarms, trackers, dashcams) and see if the code clears
- 4. Check earth strap from engine to chassis and engine to battery negative for corrosion
- 5. If voltage and connections check out, the BSI itself is the next suspect, that's a workshop diagnosis with PSA-specific tools (Diagbox or Lexia)
Common questions about C1602
Why are French cars so fussy about battery voltage? +
PSA group cars (Citroen, Peugeot, DS) rely heavily on the BSI as a central computer that talks to every other module via a multiplex network. The BSI is more sensitive to low voltage than equivalent computers in other makes, a 12.0V battery that would start a Ford fine can throw multiple BSI fault codes on a Citroen. Always rule out battery and charging issues first on a French car.
I just changed the battery, why didn't the code clear? +
On many PSA cars the new battery needs to be 'registered' to the BSI using Diagbox or Lexia. Without registration, the BSI runs a charging strategy designed for the old battery, which can cause communication faults and fail to clear stored codes. Cost £20-£50 at an independent French specialist.
Will the car still drive with C1602? +
Often yes, but with reduced functionality. Some warning lights remain on, certain comfort features may not work, and the car may not start reliably. Treat it as get-it-checked promptly rather than continue driving indefinitely. Confirm with a mechanic.
Manufacturer-specific notes
Some manufacturers publish additional definitions or variations for this code. Always cross-check with your vehicle's own service documentation.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →