Warning for left brake light + brake system failure, only when

DS Automobiles DS 4 & DS 4 CROSS
1

Had my totally new car for two weeks now covering roughly 2000km.
Last Friday it started firing intermittent warnings for the rear brake light at startup.
During Sunday it advanced to raising a warning for bra system malfunction, still only at startup.
Thought that I would record the fault and send it to my workshop. Took my phone, started recording and pushed “Start”… No fault!? Did the same thing over and over again without being able to replicate the fault while recording.
Gave up and thought that it only was a glitch.

Yesterday I got the fault directly when I started the car, turned car off and started again while recording. No fault!!!
Turned the car off, connected my USB cable for charging and started the car again - Error right away…
At that moment I started thinking of when I brought my USB cable to my car… Last Friday… And every time I was going to record the fault I removed the charging cable :rofl:
At the evening I tried again without phone connected - no error, with phone connected - error.

I guess that my phone uses so much power when charging that it messes with the sensitive CAN system.

Do you guys have any other ideas?

Note. It doesn’t actually have any faults with neither brake light or system, fault message disappears after a few seconds and everything works as it should.

2

Does it happen when You keep the cable contected but without the Phone attached to it?

3

Only when phone is connected and not fully charged.
But - now it didn’t happen when I started the car with phone connected…

4

Update regarding this,
Yesterday I was entering a car wash which pulls the vehicle through.
While waiting for the first rollers to get contact with front wheels I got the fault again.
This time without phone connected, in addition to “Warning left brake light” I got a “Warning! Brake system failure after collision”.
This fault code would stick through the entire length of the car wash (5 minutes perhaps).
In the instant I got the ready for leaving the wash, pressing brake pedal and shifting to “D” fault disappeared.

I’ll contact my dealer about this, no need to schedule a repair at this moment but I want them to investigate if this is a individual problem or if several cars has the same “fault”.

5

Hi @Fredrik_Javerhammar

It sounds to me like there is an issue with either the rear brake light unit, or possible a sensor has been damaged or is faulty, making the car intermittently think it has been in a collision. Either way, there’s no real way to diagnose it here, it’s a visit to the dealer :frowning:

Thanks,
Alex

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