Ford Fiesta Mk8 – “Additional Security System Communication Circuit” Error After Remote Start
Posted: Mon Jul 14, 2025 7:53 am
Hi everyone,
I have a Ford Fiesta Mk8 (1.0 EcoBoost) and recently installed a remote start system, including programming a new remote key and enabling the OEM bonnet/hood sensor for security compliance.
Setup:
Remote start system with key programming (works fine)
Bonnet sensor activated and wired properly
No wiring errors or faults under normal use
What works fine:
The vehicle starts and drives normally using the key
No errors appear with normal manual ignition
Problem:
When I start the vehicle remotely, then enter the vehicle and turn the key to ON (to take over ignition), I receive this dashboard warning:
“Additional Security System Communication Circuit”
At the same time, the ECU sometimes logs:
DTC Code: P166A
This appears to be a communication issue between the PATS (Passive Anti-Theft System) and the remote start system during ignition takeover.
I have a Ford Fiesta Mk8 (1.0 EcoBoost) and recently installed a remote start system, including programming a new remote key and enabling the OEM bonnet/hood sensor for security compliance.
Setup:
Remote start system with key programming (works fine)
Bonnet sensor activated and wired properly
No wiring errors or faults under normal use
What works fine:
The vehicle starts and drives normally using the key
No errors appear with normal manual ignition
Problem:When I start the vehicle remotely, then enter the vehicle and turn the key to ON (to take over ignition), I receive this dashboard warning:
“Additional Security System Communication Circuit”
At the same time, the ECU sometimes logs:
DTC Code: P166A
This appears to be a communication issue between the PATS (Passive Anti-Theft System) and the remote start system during ignition takeover.