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6.1 Anti-Lock Brake System _ABS_ Contents

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					6.1            Anti-Lock Brake System (ABS)                                                               Contents

 6.1         Model 129 (CFI only)




                                                                                         Page
Diagnosis
Complaint Related Diagnostic Chart                    ...................                11/1

Electrical Test Program
Component Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .            21/1
Preparation for Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .         22/1
Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   23/1




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                            6.1 ABS         C/1
6.1          Anti-Lock Brake System (ABS)                                                                                                             Model 129

 Diagnosis - Complaint Related Diagnostic Chart




Complaint/Problem                                      Possible cause                                            Test step/Remedy 1)


With light brake pedal applications, the brake pedal Voltage at vehicle speed sensor too low, vehicle             23 O 8.0-13.0, 17.0, 20.0, 23,01)
pulsates shortly before the vehicle comes to a       speed sensor cable has intermittently open circuit
stop.

ABS malfunction indicator lamp comes on and            Speed sensor wire interrupted                              23 O 8.0-13.0, 17.0, 20.0, 23.01)
stays on while driving

ABS malfunction indicator lamp comes on and            Battery voltage < 11 V, too many electrical                23 O 3.0
goes out again while driving                           consumers in operation, poor ground

ABS malfunction indicator lamp is on, charge           Generator defective (1 diode)                             Test generator
indicator lamp is off

ABS malfunction indicator lamp and charge              Generator defective (2 diodes)                            Test generator
indicator lamp are on

ABS malfunction indicator lamp does not go out         ABS control module (N30) connector not connected           23 O 1.0, 3.0
when engine is started                                 Poor contacts in control module connector
                                                       Overvoltage protection relay module defective, fuse
                                                       blown
ABS malfunction indicator lamp does not light up       Diode in solenoid valve relay defective, bulb defective    23 O 7.0
with ignition on

Return/pressure pump motor with ignition key           Return/pressure pump rely (A7k2) stuck closed             Check return/pressure pump relay (A7k2)
removed

ABS malfunction indicator lamp comes on at higher Rear axle vehicle speed sensor or toothed wheel                 23 O 12.0, 13.0, 23.0
speeds (approx. 35 mph) and stays on              defective or damaged
1)    Observe Preparation for Test, see 22.




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                                6.1 ABS                11/1
6.1          Anti-Lock Brake System (ABS)                                Model 129

 Electrical Test Program - Component Locations




 Figure 1
 5           Brake booster with tandem master brake cylinder
 A1e17       ABS malfunction indicator lamp
 A7          ABS hydraulic unit
 K1/1        Overvoltage protection relay module
             (87E, 7-pole)
 L6          Rear axle vehicle speed sensor
 L6/1        Left front axle vehicle speed sensor
 L6/2        Right front axle vehicle speed sensor
 N30         ABS control module
 S2/1        Ignition/starter switch
                                                                            P42-0067-57




b Diagnostic Manual • Chassis and Drivetrain • 02/93           6.1 ABS          21/1
6.1           Anti-Lock Brake System (ABS)                                                                                                         Model 129
    Electrical Test Program - Preparation for Test



•      For all test steps performed with ignition ON, the LED m must light          Note:
       up, i.e. battery voltage O.K.                                                The entire ABS test must be performed after any repairs or other work on
•      When testing , all other electrical consumers must be turned off.            either the ABS system or the brake system.
•      For O 23.0 - 25.0 the rear wheels must be raised off the ground.
                                                                                    Note:
Note:                                                                               It is assumed that the technician is capable of testing switches, relays,
Unscrew locking tab (arrow, 23 Fig. 13) from                                        lamps, connectors and wires for proper operation without further
ABS-adapter plug 126 589 09 21 00.                                                  instructions.


a           Never drive the vehicle with the ABS-adapter (07) connected!


Special Tools




               126 589 09 21 00                            201 589 00 99 00

               35-pin socket box                        Electrical connecting set


Equipment
    Multimeter 1)                                                                                    Fluke models 23, 83, 85, 87
                                                                                                     SUN DMM-5
1)     Available through the MBUSA Standard Equipment Program.



b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                             6.1 ABS                        22/1
6.1          Anti-Lock Brake System (ABS)                                 Model 129


 Electrical Test Program - Preparation for Test

 Connection Diagram –
 Multimeter to ABS-Adaptor



 M
 Unplug connector to ABS control module
 (N30) with ignition switched OFF
 (Figure 1)




 Figure 1
  01          Vehicle wiring harness (ABS/ASR control module)
  06          Multimeter
  07          ABS-adaptor         126 589 09 21 00
                                                                             P42-0022-57




b Diagnostic Manual • Chassis and Drivetrain • 02/93            6.1 ABS          22/2
6.1          Anti-Lock Brake System (ABS)                                                                                            Model 129

 Electrical Test Program - Test




Test step      Test scope                              Test connection   Test condition        Nominal value    Possible cause/Remedy
      Adaptor
      position

O 1.0           1 Overvoltage protection relay         -                 Ignition: OFF         LED              Check overvoltage protection relay
                   module (87E, 7-pole) (K1/1)                                                 All: OFF         module (K1/1) (Figure 1).


O 2.0           1 Solenoid valve relay (A7k1)          -                 Ignition: OFF         LED              Check solenoid valve relay (A7k1)
                                                                                               All: OFF         (Figure 2).


O 3.0           1 Overvoltage protection relay         Connect c         Ignition: ON          11 - 14 V       Wiring interrupted, Battery not
                   module (87E, 7-pole) (K1/1)         to C                                    LED             properly charged,
                                                                                               m: ON           Check fuse for overvoltage
                                                                                               p: ON           protection relay module (K1/1),
                                                                                                               Check ABS malfunction indicator
                                                                                               ABS malfunction lamp (A1e17),
                                                                                               indicator lamp: Check solenoid valve relay (A7k1),
                                                                                               ON              Check overvoltage protection relay
                                                                                                               module (K1/1).


O 4.0           1 Generator,                           -                 Engine: RUN BRIEFLY   LED              Wiring interrupted,
                   circuit 61                                                                  p: OFF           Terminal block (terminal
                                                                                                                30/30Ü/61e/87L) (X4/10) poor
                                                                                                                contact (Figure 4),
                                                                                                                Generator or generator wiring
                                                                                                                defective.




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                               6.1 ABS                      23/1
6.1          Anti-Lock Brake System (ABS)                                                                                              Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection   Test condition        Nominal value     Possible cause/Remedy
      Adaptor
      position

O 4.0           1 Stop lamp switch (S9/1)              -                 Ignition: ON          LED               Wiring interrupted,
                                                                         Depress brake pedal   n: ON             check stop lamp switch (S9/1).


O 6.0           2 Solenoid valve relay (A7k1)          -                 Ignition: ON          LED               Terminal block (terminal)
                                                                                                                 30/30U/61e/87L) (X4/10) poor
                                                                                               m : ON            contact (Figure 4),
                                                                                               p : ON            Wiring interrupted,
                                                                                               l: ON             Check solenoid valve relay (A7k1)
                                                                                                                 (Figure 2)
                                                                                               Malfunction
                                                                                               indicator lamp:
                                                                                                  OFF

O 7.0           3 Diode in solenoid valve relay        Connect c         Ignition: ON          0.4 - 1.5 V       Check solenoid valve relay (A7k1).
                   (A7k1)                              to C                                    LED
                                                                                               m : ON
                                                                                               p : ON


O 8.0           4 Left front axle vehicle speed        Connect b         Ignition: ON          0.85 - 2.3 k]     Wiring interrupted,
                   sensor (L6/1)                       to C                                                      Check left front axle vehicle speed
                   Internal resistance                                                                           sensor (L6/1).




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                 6.1 ABS                      23/2
6.1          Anti-Lock Brake System (ABS)                                                                                        Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection   Test condition    Nominal value   Possible cause/Remedy
      Adaptor
      position

O 9.0           4 Left front axle vehicle speed        Connect b         Ignition: ON      > 20 k]         Check left front axle vehicle speed
                   sensor (L6/1)                       to C              Press button: o                   sensor (L6/1).
                   Insulation resistance


O 10.0          5 Right front axle vehicle speed Connect b               Ignition: ON      0.85 - 2.3 k]   Wiring interrupted,
                  sensor (L6/2)                  to C                                                      Check right front axle vehicle speed
                   Internal resistance                                                                     sensor (L6/2).



O 11.0          5 Right front axle vehicle speed Connect b               Ignition: ON      > 20 k]         Check right front axle vehicle speed
                  sensor (L6/2)                  to C                    Press button: o                   sensor (L6/2).
                   Insulation resistance


O 12.0          6 Rear axle vehicle speed              Connect b         Ignition: ON      0.6 - 1.6 k]    Wiring interrupted,
                   sensor (L6)                         to C                                                Check rear axle vehicle speed
                   Internal resistance                                                                     sensor (L6).




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                           6.1 ABS                     23/3
6.1          Anti-Lock Brake System (ABS)                                                                                       Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection   Test condition    Nominal value   Possible cause/Remedy
      Adaptor
      position

O 13.0          6 Rear axle vehicle speed              Connect b         Ignition: ON      > 20 k]         Check rear axle vehicle speed
                   sensor (L6)                         to C              Press button: o                   sensor (L6).
                   Insulation resistance


O 14.0          8 Left front axle solenoid valve       Connect b         Ignition: OFF     0.7 - 2.2 ]     Wiring interrupted,
                   (A7y2)                              to C              Press button: o                   Check ABS hydraulic unit (A7).
                   Internal resistance


O 15.0          9 Right front axle solenoid            Connect b         Ignition: OFF     0.7 - 2.2 ]     Wiring interrupted,
                   valve (A7y2)                        to C              Press button: o                   Check ABS hydraulic unit (A7).
                   Internal resistance


O 16.0        10 Rear axle solenoid switch             Connect b         Ignition: OFF     0.7 - 2.2 ]     Wiring interrupted,
                   (A7y3)                              to C              Press button: o                   Check ABS hydraulic unit (A7).
                   Internal resistance




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                          6.1 ABS                       23/4
6.1          Anti-Lock Brake System (ABS)                                                                                                        Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection     Test condition                Nominal value     Possible cause/Remedy
      Adaptor
      position

O 17.0          4 Left front axle speed sensor         Connect f           Raise vehicle               f 0.1 V~            Open circuit or wires connected
                   (L6/1)                              to C                Ignition: ON                                    incorrectly,
                   Voltage                                                 Turn wheel at approximately                     Excessive wheel bearing play,
                                                                           one revolution/second.                          Check left front axle vehicle speed
                                                                                                                           sensor (L6/1).

O 18.0          8 Left front axle solenoid valve               s           Vehicle raised                LED               Ground (ABS hydraulic unit bracket)
                   (A7y1)                              remains connected   Ignition: ON                  m: ON             (W14) poor contact (Figure 10),
                   Pressure retention                                      Turn wheel at approximately   p: ON             Brake lines on ABS hydraulic unit
                                                                           one revolution/second .       l: ON             (A7) reversed,
                                                                           Press switch: “P=”.           n: ON             Wires reversed,
                                                                           Depress brake pedal.          Wheel must be     Check ABS hydraulic unit (A7).
                                                                                                         able to rotate.




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                           6.1 ABS                    23/5
6.1          Anti-Lock Brake System (ABS)                                                                                                       Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection     Test condition                Nominal value     Possible cause/Remedy
      Adaptor
      position

O 19.0          8 Left front axle solenoid valve               s           Vehicle raised                LED               Ground (ABS hydraulic unit bracket)
                   (A7y1)                              remains connected   Ignition: ON                  m: ON             (W14) poor contact (Figure 10),
                   Pressure reduction                                      Depress brake pedal.          p: ON             Check return/pressure pump relay
                                                                           Press switch: “P ”.           l: ON             (A7k2) (Figure 2),
                                                                           Turn wheel at approximately   q: ON             Check ABS hydraulic unit (A7)
                                                                           one revolution/second         n: ON
                                                                                                         Wheel must be
                                                                                                         able to rotate.

O 20.0          5 Right front axle speed sensor Connect f                  Raise vehicle               f 0.1 V~            Open circuit or wires connected
                  (L6/2)                        to C                       Ignition: ON                                    incorrectly,
                   Voltage                                                 Turn wheel at approximately                     Excessive wheel bearing play,
                                                                           one revolution/speed                            Check right front wheel speed
                                                                                                                           sensor (L6/2).

O 21.0          9 Right front axle solenoid                    s           Vehicle raised                LED               Wires connected incorrectly,
                   valve (A7y2)                        remains connected   Ignition: ON                  m: ON             Ground (ABS hydraulic unit bracket)
                   Pressure retention                                      Turn wheel at approximately   p: ON             (W14) poor contact (Figure 10),
                                                                           one revolution/second .       l: ON             Check ABS hydraulic unit (A7).
                                                                           Press switch: “P=”.           n: ON
                                                                           Depress brake pedal.          Wheel must be
                                                                                                         able to rotate.




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                          6.1 ABS                    23/6
6.1          Anti-Lock Brake System (ABS)                                                                                                       Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection     Test condition                Nominal value     Possible cause/Remedy
      Adaptor
      position

O 22.0          9 Right front axle solenoid                    s           Vehicle raised                LED               Ground (ABS hydraulic unit bracket)
                   valve (A7y2)                        remains connected   Ignition: ON                  m: ON             (W14) poor contact (Figure 10),
                   Pressure reduction                                      Twice depress brake pedal.    p: ON             Check return/pressure pump relay
                                                                           Press switch: “P ”.           l: ON             (A7k2) (Figure 2),
                                                                           Turn wheel at approximately   q: ON             Check ABS hydraulic unit (A7)
                                                                           on revolution/second .        n: ON
                                                                                                         Wheel must be
                                                                                                         able to rotate.

O 23.0          6 Rear axle vehicle speed              Connect f           Raise vehicle               f 0.1 V~            Wires interrupted,
                   sensor (L6)                         to C                Ignition: ON                                    Rear axle vehicle speed sensor
                   Voltage                                                                                                 dirty,
                                                                           Turn wheel at approximately
                                                                                                                           Check rear axle vehicle speed
                                                                           one revolution/second.                          sensor (L6).




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                          6.1 ABS                    23/7
6.1          Anti-Lock Brake System (ABS)                                                                                                       Model 129


 Electrical Test Program - Test


Test step      Test scope                              Test connection     Test condition                Nominal value     Possible cause/Remedy
      Adaptor
      position

O 24.0        10 Rear Axle solenoid valve                      s           Vehicle raised                LED               Wire connected incorrectly,
                   (A7y3)                              remains connected   Ignition: ON                  m: ON             Ground (ABS hydraulic unit bracket)
                   Pressure retention                                      Turn wheel at approximately   p: ON             (W14) poor contact (Figure 10),
                                                                           one revolution/second.        l: ON             Brake lines on hydraulic unit
                                                                           Press switch: “P=”.           n: ON             interchanged,
                                                                           Depress brake pedal.          Wheel must be     Check ABS hydraulic unit (A7).
                                                                                                         able to rotate.

O 25.0        10 Left rear axle solenoid valve                 s           Vehicle raised                LED               Ground (ABS hydraulic unit bracket)
                   (A7/3y3)                            remains connected   Ignition: ON                  m: ON             (W14) poor contact (Figure 10),
                   Pressure reduction                                      Apply brake pedal.            p: ON             Return/pressure pump relay (A7k2)
                                                                           Press switch: “P ”.           l: ON             (Figure 2),
                                                                           Turn wheel at approximately   q: ON             ABS/ASR hydraulic unit (A7/3).
                                                                           one revolution/second.        n: ON
                                                                                                         Wheel must be
                                                                                                         able to rotate.




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                          6.1 ABS                    23/8
6.1          Anti-Lock Brake System (ABS)                                                                                                                    Model 129


 Electrical Test Program - Test




                                               P54-2043-13                                           P42-2051-13                                                 P42-2053-13
Figure 1                                                     Figure 2                                              Figure 3

K1/1        Overvoltage protection relay module              A7k1       Solenoid valve relay                       L6/1       Left front axle vehicle speed sensor
            (87E, 7-pole)                                    A7k2       Return/pressure pump relay                 X62/14     Left front axle vehicle speed sensor connector
N30         ABS control module                                                                                                (axle spindle)




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                                  6.1 ABS                          23/9
6.1          Anti-Lock Brake System (ABS)                                                                                                                           Model 129


 Electrical Test Program - Test




                                               P54-2039-13                                                  P54-2058-13                                                 P42-2053-13
Figure 4                                                      Figure 5                                                    Figure 6

X4/10       Terminal block (terminal 30/30Ue/61e/87L)         X62/7      Left front axle vehicle speed sensor connector   X62/14     Left front axle vehicle speed sensor connector
X62/6       Right front axle vehicle speed sensor connector              (component compartment)                                     (axle spindle)
            (Component Compartment)




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                                         6.1 ABS                         23/10
6.1          Anti-Lock Brake System (ABS)                                                                                                                          Model 129


 Electrical Test Program - Test




                                               P42-2050-13                                                P54-2060-13                                                 P54-2040-13A
Figure 7                                                     Figure 8                                                   Figure 9

X62/15      Right spindle axle vehicle speed sensor          X47        Rear axle vehicle speed sensor harness          X62/8      Rear axle multiple circuit junction connector
            connector                                                   connector
            (axle spindle)                                              (2-pole)




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                                       6.1 ABS                          23/11
6.1          Anti-Lock Brake System (ABS)                                                                                                                                  Model 129


 Electrical Test Program - Test




                                                  P54-2048-13                                                     P42-2057-13                                                    P54-2043-13A
Figure 10                                                        Figure 11                                                      Figure 12

W3          Ground, left front wheelhousing (at ignition coil)   X62/8       Rear axle multiple circuit junction connector      X11/4       Diagnostic connector
W14         Ground, ABS hydraulic unit bracket                                                                                              (diagnostic trouble code, 16-pole)
                                                                                                                                X30/1       Multi-function block connector




b Diagnostic Manual • Chassis and Drivetrain • 02/93                                                                                                6.1 ABS                          23/12
6.1          Anti-Lock Brake System (ABS)                              Model 129


 Electrical Test Program - Test




                                               P42-2079-13
Figure 13

ABS Adapter plug




b Diagnostic Manual • Chassis and Drivetrain • 02/93         6.1 ABS       23/13

				
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