Starting issue, transponder aerial?

KERNOWJOE87

MEMBER
2018 CITROEN C3
1.2L
AUTOMATIC
6,000 MILES

I bought this car last year and started experiencing problems with it not starting. This would be completely random and was happening regularly. It happened in hot and cold weather and also happened after not driving the car for 5 minutes or even overnight. The problem continued and I took it into the dealership. It's been there for 4 months and has been to 4 different car garages, one of which was a Citroen garage, all of which couldn't diagnose the problem, despite the error codes.

I've been messaged today to say they've fitted a transponder aerial and all is now okay.

This is great and all, but 4 months, 4 garages and not one of them suggested this. Also, if this was the issue, would it not have been flagged up when they plugged it in for a diagnosis?

Thursday, January 16th, 2025 AT 6:20 AM

1 Reply

BORIS K

MECHANIC
836 POSTS

Hello,

Happy for you that the vehicle is finally sorted.

There should have been transponder key related fault codes set in the BCM, Body Control Module.

Immobilizer system layout

BCM
ECM
Ignition Key/Key Fob with integrated Transponder
Immobilizer Antenna
Steering Column Control Module

BCM acts as a communications hub for immobilizer functions. The BCM incorporates the software module which controls the immobilizer function. This area of the BCM also holds the coded data for interaction with both key and engine ECM.

Cheers, Boris

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Thursday, January 16th, 2025 AT 8:16 AM