Antilock Brake System (ABS)
Antilock braking system is an enhanced braking system that monitors individual wheel rotation and prevents the wheels from locking up while stopping.
Locked wheels provide inefficient braking and sacrifice directional control, so ABS shortens stopping distances in most conditions and allows the driver to steer even when panic braking.
The federal government began requiring ABS on all new cars starting with the 2012 model year. Pulsation in the brake pedal can startle the uninitiated, but it is a sign of the ABS properly doing its job.
In structure, ABS is similar to a conventional braking system, but its components may need repair, starting with electronic wheel sensors at each wheel or at the differential, the computer brain called the control module, and a valve assembly and pump.
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Diagnostic Trouble Codes (DTC)
When the ABS warning light in the Instrument Panel remains ON, the EHCU (Electronic Hydraulic Control Unit) stores the DTC and disables the ABS.
DTC display:
When the DTC display activated the ABS warning light will blink. The code is a Double-digit display. By counting the number of times the ABS warning light flashes, the DTC code can be determine.
See the table below for the DTC
Descriptions.
The first code displayed is the normal DTC 12 and signifies the start and stop of a DTC flash sequence. It is displayed three times.
If any other DTCs are stored in the EHCU they will be displayed three times. If no other DTCs have been stored then the display of DTC 12 will be repeated 3 times.
The sequence repeats for 5 minutes or until the ignition switch is switch OFF or the jumper is removed.
Starting the DTC Display
- The vehicle must be stopped and the brake pedal is not pressed in.
- The ignition switch must be in the off position.
- Install a jumper fromthe DLC terminal 12 to terminal 4 (see the diagram below).
- Turn on the Ignition Switch.
Erasing the Codes
During the first 3 seconds after the ignition switch is switched to the ON position, press the brake pedal 6 times. Actuation of the brake pedal switch during the EHCU self-diagnosis startup period clears the memory of the EHCU.
Additionally, the EHCU memory will be cleared upon driving the vehicle above 8 mph and no faults detected by the EHCU.
Diagnostic Trouble Codes (DTC)
Code Flash out | Diagnosis | Description |
---|---|---|
12 | – | – |
13 | C0285 | 2 WD Controller in 4WD Vehicle Controller |
14 | C0271 | RAM read/write error |
14 | C0272 | ROM checksum error |
14 | C0270 | ALU function error |
14 | C0273 | Inoperative isolation item |
14 | C0284 | Loop time overrun |
15 | C0277 | Low ignition voltage |
15 | C0278 | High ignition voltage |
17 | C0269 | Excessive dump time |
18 | C0274 | Excessive isolation time |
21 | C0276 | G-Sensor Failure |
22 | C0281 | Brake switch Failure |
24 | C0282 | Open or shorted 4×4 input signal (4WD only) |
32 | C0267 | Open motor circuit or shorted ECU output |
32 | C0268 | Stalled motor or open ECU output |
35 | C0265 | Open relay circuit |
35 | C0266 | Shorted relay circuit |
41 | C0245 | FL Open isolation solenoid or shorted ECU output |
41 | C0247 | FL Shorted isolation solenoid or open ECU output |
42 | C0246 | FL Open dump solenoid or shorted ECU output |
42 | C0248 | FL Shorted dump solenoid or open ECU output |
43 | C0241 | FR Open isolation solenoid or shorted ECU output |
43 | C0243 | FR Shorted isolation solenoid or open ECU output |
44 | C0242 | FR Open dump solenoid or shorted ECU output |
44 | C0244 | FR Shorted dump solenoid or open ECU output |
45 | C0251 f^ • | Rear Open isolation solenoid or shorted ECU output |
45 | C0253 | Rear Shorted isolation solenoid or open ECU output |
46 | C0252 | Rear Open dump solenoid or shorted ECU output |
46 | C0254 | Rear Shorted dump solenoid or open ECU output |
51 | C0225 | FL Open or shorted sensor |
52 | C0221 | FR Open or shorted sensor |
53 | C0235 | Rear Open or shorted sensor |
61 | C0226 | FL Missing sensor signal |
61 | C0227 | FL Sensor signal dropout |
62 | C0222 | FR Missing sensor signal |
62 | C0223 | FR Sensor signal dropout |
63 | C0236 | Rear Missing sensor signal |
63 | C0237 | Rear Sensor signal dropout |
64 | C0229 | Simultaneous dropout of front sensor signal |
65 | C0238 | Wheel speed error |
– Additional –
This file contains information transposed from the BMW Car Club of Bulgaria forum site (Errors and omissions excluded) –
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