C5 recurring error "Speed Control System Faulty"

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C5and307inOz
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C5 recurring error "Speed Control System Faulty"

Post by C5and307inOz »

My 2006 C5 2.2 HDI Bi-Turbo regularly comes up with the message "Speed Control System Faulty". Interestingly this occurs in the same places on my regular trips. It happens when I leave two particular roundabouts and accelerrate. The cruise control and speed limiters are both disabled and also the first turbo seems to stop working (a form of limp mode?). If I stop and turn off the ignition for 5 minutes everything returns to normal. I have replaced the brake switch with the modified version to no effect. Any ideas?
C5and307inOz
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Re: C5 recurring error "Speed Control System Faulty"

Post by C5and307inOz »

I now suspect the yaw sensor. Anyone know where this is located?
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Post by addo »

Yaw sensors seem to often be low down, mid-wheelbase. I'd look on the floorpan under front seats or beneath the rear seat cushion.

Citroën changed the sensor type around RPO 10100 to an "inertia" device - think iPhone etc. This makes me presume its pedecessor worked on a gyroscopic mass arrangement.

As to Lexia and C5 faults - I have noted a decent number of faults in steering angle sensors with early C5s - can't be sure it carries through to C5-II and X7 versions. Along with the radio aerial fault, it is one of two you're almost guaranteed to detect on any car plugged in.
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