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self braking 996 4S 2002 :-( Faultcodes 4340 4460 4276)

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Hello everybody! My 2002 996 4S has a strange problem.....

While i left home two weeks ago, i first noticed that the brakepedal felt hard... thereafter i noticed initially that the car didnt seem to roll easily.... it felt like there was a little bit off brake power applied to the wheels.....

Entering the highway, at a speed op 70 miles/hr the wheel started to shiver , initially a little bit, but quickly increasing in force. I thought it was a flat tire, so i stopped..... When speed decreased i noticed that the car was braking by itself. After the car came to a full stop, and i checked the tires ( no flat tires) i tried to drive away but i couldnd, the wheels were locked..... I had to call for a tow a way truck...... I saw three warnings on the dash, amber: psm failure, drive to workshop, amber: ABS failure and red: WARNING brake distribution......

the strange thing however: after the car was delivered to the dealer it seemed to be ok..... No more warnings and the wheels were free again.... I noticed that brakefluid was forced out of the reservoir a little bit.....

The dealer is looking into the problem now for two weeks already and they still have no glue what the problem is.... It comes back after a few minutes of driving the car....





Does anybody have an idea? I hope somebody recognice the problem........

Thanx for reading this post anyway!


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Fault code 4276 -- Valves voltage supply

Possible cause of fault

- Fuse E9 faulty

- Short circuit or open circuit in the B+/ground supply to the control unit

- Hydraulic power unit faulty

Fault code 4340 -- Stop light switch

Possible cause of fault

- Fuse E9 faulty

- Short circuit or open circuit in the B+/ground supply to the control unit

- Hydraulic power unit faulty

Fault code 4460 -- Pressure sensor

Possible cause of fault

- Short circuit to ground/8+ or open circuit

- Plug connection on stop light switch faulty

- Incorrect adjustment of the stop light switch

- Wiring/plug connection between pressure sensor and control module faulty

- Pressure sensor faulty

I would start with fuse E9 - then reset the codes and see which come back.

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  • 1 year later...

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