Brake Light Circuit?

[IvanHansen]

Sometimes I get a "Brake Light Circuit" message on my OBC. Completely random and the brake lights works just fine, despite the message.

Could it be the brake light switch?

Batteries, wiring etc. is fine.

[koenig d]

this happens on mine. Iv'e been told the wireing has degraded near the boot hinge. if you pull back the outer sleave covering you may find broken or damaged wires.
also check if the bulbs are OEM apparently they work better than others

[TxGR8White]

Either the Brake light switch or the LKM.
BRAKE LIGHT CIRCUIT is different then BRAKE LIGHT FAIL (which is what koenigd is talking about).
Had this on a 1996 850Ci - turned out to be the LKM.

[IvanHansen]

Thanks for the fast response.

Hey Koenig it's not the wiring, checked and fixed that a while ago .

What is the LKM and where is it placed (I'm still struggling to understand all the abbreviations everyone else seems so familiar with)

[koenig d]

http://www.5series.net/information/B...reviations.pdf
just for you IVAN. This is for the 5 series there may be a few differances.

[TxGR8White]

http://www.5series.net/information/B...reviations.pdf
just for you IVAN. This is for the 5 series there may be a few differances.

The one abbreviation he needs is not on the list (no LKM in the 5-series).

The LKM is the Light Control Module. It is located under the dashboard left side of the car (driver side in US, passenger side in UK) in a plastic carrier with 2 other modules (EKM and the General Module). The LKM is the top most module and has a white and a black connector on it.

[Frankie]

I would bet the problem lies in your brake light switch, located up under the dash, high up on the brake pedal arm. My E36 throws this warning about every 3 years - then it's time for a new switch. Easy fix.

[koenig d]

ah I found the 1 I was looking for.
This list of abbreviations is also handy:-

BMW abbreviations with German translations (sometimes it explains the abbreviation)


A - Processed Vehicle Speed Signal
AB - Airbag
ABS - Anti-Lock Braking System (Antiblockiersystem)
ACC - Active Cruise
A/D - Analog to Digital
ADS - Engine Intake Air Control
ADV - Windshield Wiper Pressure Control
AFS - Active Front Steering
AGS - Adaptive Transmission Control
AHPS - Advanced Head Protection System
AIC - Automatic Interval Control (Automatic Intervall Control/Regensensor)
AITS - Advanced Inflatable Tubular Structure see AHPS
AKS - Active Head Restraint System (Aktive Kopfstutze)
ARS - Active Roll Stabilization (Aktive Rollstabilisierung)
ASC - All Season Control
ASC+T - ASC + Traction
ASE - Advanced Safety Electronics
ASK - Audio System Controller (Audio-System-Kontroller)
AST - Slip Control (Marketing)
AUC - Automatic Air Recirculation
AWL - Airbag Warning Lamp

B - Benzine (used in engine codes)
BC - Board Computer
BLS - Brake Light Switch (Bremslichtschalter)
BMBT - Board Monitor
BMW - Bavarian Motor Works (Bayerische Motoren Werke)
BST - Battery Safety Terminal
BZM - Center Console Control Center (Bedienzentrum Mittelkonsole)

CAN - Controller Area Network
CBC - Corner Braking Control
CCM - Check Control Module
CIP - Coding Individualization and Programming
CVM - Convertible Top Module

D-Bus - Diagnosis Bus (TXD)
DDE - Digital Diesel Electronics
DIN - German Industrial Stadards (like our SAE)
DIS - Diagnosis and Information System
DISA - Differnential Intake Air Control (Differenzierte Sauganlage)
DK - Throttle Housing
DKI - Throttle Position
DME - Digital Motor Electronics
DM-TL Diagnostic Module Tank Leakage
DSC - Dynamic Stablity Control (Dynamische Stabilitats Control)
DSP - Digital Sound Processing
DTC - Diagnostic Trouble Code or Dynamic Traction Control
DWA - Theft Deterrent System
DWS - Tire Pressure Warning System

E-KAT - Electrically Heated Catalytic Converter
EBV - Electronic Brake Force Distribution (Elektronische Bremskraftverteilung)
ECO - Electronically Controlled Orifice
ECM - Engine Control Module (per SAE)
EDC - Electronic Damper Control (Elektronische Dampfer Steuerung)
EDK - Electronic Throttle Valve
EGS - Electronic Transmission Control
EH - Electronic Hydraulic
EHC - Electronic Height Control (Elektronische Hohenstands Control)
EKP - Electric Fuel Pump (Elektrische Kraftstoffpumpe)
EKM - Electronic Body Module
ELV - Electronic Steering Lock
EML - Electronic Motor Load Regulation (Electronische Motorleistungsregulierung)
EO - Component Location
EWS - Electronic Driveaway Protection (Elektronische Wegfahsperre)

FA - Vehicle Order (Fahrzeug-Auftrag)
FB - Functional Description (Funktionsbestatigung)
FBZV - Radio Frequency Locking System
FIRST - Fully Integrated Road Safety Technology

GAL - Speed Dependant Volume
GPS - Global Positioning System
GM - General Module (Grundmodul)
GMR - Yaw Moment Module
GRAV - Gewichtsreduzierter Aluminiumvorderbau (E60 Aluminum process)
GRII - Cruise Control

HDC - Hill Descent Control
HFM - Hot Film Air Mass Meter (Heibfilm-Luftmassenmesser)
HLM - Hot Wire Air Mass Meter (Hitzdraht-Luftmassenmesser)
HPS - Head Protection System
HUD - Heads Up Display

IB - Interior Lighting Control Signal
I-bus - Information Bus
IBS - Intelligent Battery Sensor
IHKA - Automatic Heating and A/C
IHKR - Regulated Heating and A/C
IHKS - Standard Heating and A/C
IKE - Instrument Cluster Electronics (Instrumentenkombination-Elektonik)
ISIS - Intelligent Safety Information System (Intelligentes Sicherheits-und Informations-System)
ISN - Individual Serial Number or Individual Control Unit Number
ITS - Inflatable Tubular Structure

KAT - Catalytic Converter
KATON - Converter Heating Signal
K-Bus - Body Bus
KBM - Body Basic Module (Karosserie-Basis-Modul)
KL - Terminal Designation (like KL15 is ignition positon on the key)
KO - Compressor "ON" Signal
Kombi- Cluster in German
KOREL - Compressor Relay Signal
KW - Crankshaft

LCM - Lamp Check Module (Lamp Kontrol Modul)
LDP - Leak Diagnosis Pump
LED - Light Emitting Diode
LEV - Low Emissions Vehicle
LIN - Local Interconnect Network
LKM - Lamp Control Module
LL - Idle or Closed Throttle Position (Leerlauf)
LRA - Vertical Headlight Aiming
LRE - Steering Wheel Electronics
LSE - Steering Column Electronics
LSM - Steering Column Memory
LSZ - Light Switching Center (Lightschaltzentrum)
LVA - Air Supply System
LWR - Vertical Headlight Aiming
LWS5 - Steering Angle Sensor

M-ASK - Multi-Audio System Controller (Multi-Audio-System-Kontroller)
MBC - Maximum Brake Control
MDK - Motorized Throttle Valve (Motorische Drosselklappe)
MFL - Multi-function Steering Wheel
MID - Multi Information Display
MoDiC - Mobile Diagnostic Computer
MOST - Media Oriented System Transport
MRS - Multiple Restraint System (Mehrfach-Ruckhaltesystem)
MRSA - Side Impact Sensor
MSR - Deceleration Slip Regulation or Engine Drag Torque Reduction (Motorschleppmomentregelung)

NVRAM - Non-Volatile Random Access Memory

OBC - On Board Computer
OBD - On Board Diagnostics
OC-3 - Occupant Classifier-3
OPPS - Optic Testing and Programming Systems (Optisches Pruf-und Programmiersystem)
OPS - Optic Programming System
ORVR - On Board Refueling and Vapor Recovery

PB - Pin Assignments
P-Bus - Periphery Bus
PDC - Park Distance Control
PTC - Positive Temperature Coefficient
PuMA - (Problem-und Mebnahmenmanagement Aftersales)
PWG - Pedal Position Sensor (Pedalwertgeber)
PWM - Pulse Width Modulation (Pulseweitenmodulation)

RAM - Random Access Memory
RDC - Tire Pressure Control (Reifen Druck Control)
RDW - Tire Pressure Warning System (Reifendruckwarnung)
RLS - Rain and Light Sensor
RM - Relay Module
RPS - Rollover Protection System
RXD - Wake-up Diagnosis Line
RZV - Direct Stationary Ignition (Rehende Zundspannungsverteilung)

SAC - Self Adjusting Clutch (Selbstnachstellende Kupplung)
SAE - Society of Automotive Engineers
SASL - Satellite A-Pillar, Left (Satellit A-Saule Links)
SASR - Satellite A-Pillar, Right (Satellie A-Saule Rechts)
SB - Fuse Assignments
SBE - Passenger Seat Occupancy Detection System (Sitzbelegungserkennung)
SBK - see BST (Safety Batterie Klemme)
SBSL - B-Pillar Satellite, Left (Satellit B-Saule Links)
SBSR - B-Pillar Satellite, Right (Satellit B-Saule Recht)
SCA - Soft Close Actuator
S/E - Send and Receive
SFZ - Center Vehicle Satellite (Satellit Fahrzueg Zentrum)
SG - Control Unit (Steuergerat)
SGM - Safety and Gateway Module (Safety Gateway Modul)
SGS - Seat Integrated Belt System (Sitzintegriertes Gurtsystem)
SHD - Sunroof Module
SIA - Service Interval Indicator (Service-Intervall-Anzeige)
SIM - Safety and Information Module (sicherheits-Informationsmodul)
SLP - Secondary Air Pump (Sekundar-Luft-Pumpe)
SMBF - Seat Module, Passenger (Sitzmodul Beifahrer)
SMFA - Seat Module, Driver (Sitzmodul Fahrer)
SMG - Sequential Manual Gearbox (Sequenzielles M Getriebe or Sequenzielles Manualles Schalt-Getriebe)
SP - Schematic
SRS - Supplemental Restraint System
SSBF - Seat Satellite, Passenger (Satellit Beifahrersitz)
SSFA - Seat Satellite, Driver (Satellite Fahrersitz)
SSH - Seat Satellite, Rear
ST - Connector Views
STVL - Door Satellite, Front Left (Satellit Tur Vorne Links)
STVR - Door Satellite, Front Right (Satellite Tur Vorne Recht)
SULEV - Super Ultra-Low Emissions Vehicle
SZL - Steering Column Switch Center (Schaltzentrum Lenksaule)
SZM - Switching Center Console (Schaltzentrum Mittelkonsole)

TCU - Telematics Control Unit
TD - Engine Speed Signal
ti - Injector "ON" time
TL - Part Throttle
TLEV - Transitional Low Emission Vehicle
TMBF - Door Satellite, Passenger Door (Tur Modul Beifahrer)
TMFA - Door Satellite, Driver (Tur Modul Fahrer)
TRS - Battery Isolation Switch
TSH - Door Lock Heating System
TU - Technical Update (like with engine codes)
TXD - Transmitting Diagnosis Line

URSS - see RPS (Uberroll Shultz System)

VANOS - Variable Camshaft Control (Variable Nocken-Steuerung or Variable Nockenwellen-Steuerung)
VL - Full Load - Wide Open Throttle (WOT)
VVT - Variable Valve Timing (Variable Ventiltrieb)

WK - Converter Lock-up Clutch

ZAE - Central Activation Electronics (Zentrale Auslose Elektronik)
ZCS - Central Coding Key
ZGM - Central Gateway Module (Zentral Gateway Modul)
ZKE - Central Body Electronics (Zentrale Karosserieelektronik)
ZV - Central Locking System
ZVM - Central Locking Module
ZWD - Idle Control Valve (Zweiwicklungs Leerlauf-Drehsteller)

[TxGR8White]

Iceman:
Maybe this should be a "sticky"...

[IvanHansen]

You guys are excellent - thanks a lot

[IcemanBHE]

Good idea.

Dave, would please repost #8 in the DIY forum please.

[NickF]

I just had this and it was the switch. I think BMW make them out of chocolate.

Not sure whether the steering wheel is correctly stationed in your country but the switch is on the left side (US drivers side) regardless.

[IvanHansen]

Update.
I have changed the brake light switch and so far no error messages, but I will keep you posted.
PIA to get the old one out by the way .

[rcrad6653]

Yes, both the brake and clutch switch are a pita to get out the first time, till you figure out how the germans were thinking. They are masters of the art of attachment so that something is not only extremely secure, but provides the ability to easily break it getting it off and give you maximum frustration in the process.... what a deal

To all: If you ever have to change one of these switches, once you get up under there and are uncomfortably working backwards and over your head, you pry upward on the lip of the piece that surrounds the switch plunger.... you will feel it release. It then provides enough clearance at the bottom of it to push in the two side tabs holding it to the bracket. Installation is the reverse whereby you push that surround piece downward till it clicks.

[TwoEagle]

Yes, both the brake and clutch switch are a pita to get out the first time, till you figure out how the germans were thinking. They are masters of the art of attachment so that something is not only extremely secure, but provides the ability to easily break it getting it off and give you maximum frustration in the process.... what a deal

To all: If you ever have to change one of these switches, once you get up under there and are uncomfortably working backwards and over your head, you pry upward on the lip of the piece that surrounds the switch plunger.... you will feel it release. It then provides enough clearance at the bottom of it to push in the two side tabs holding it to the bracket. Installation is the reverse whereby you push that surround piece downward till it clicks.

Yes...I was up there the other day disconnecting brakelightswitch in search of my TFSM. Not very easy to see so this info is nice... maybe it`s more understandable if you study the NEW switch before attempting to remove the old one...just an idea

[Tomcat BMW]

Does anyone have the Part # for the brakelightswitch ...and a good vendor?
1991 BMW 850i.
Thanks!