Page 6 of 57
38C-6V1 MR-376-X76-38C000$040.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Operating diagram38C
ABS BOSCH 8.1
Vdiag No.: 18
1 ABS computer 6 Front wheel speed sensor
2 Brake switch 7 Rear wheel speed sensor
3 After ignition supply 8 Diagnostic socket
4 Permanent supply 9 Vehicle speed signal
5 Earth 10 Fault warning lights on the instrument panel
Electric circuit Hydraulic circuit
Page 7 of 57

38C-7V1 MR-376-X76-38C000$050.mif
38C
ABS BOSCH 8.1
Vdiag No.: 18
On this vehicle, the main functions of the ABS are as follows:
● electronic distribution of braking between front and rear by controlling skidding of the rear wheels,
● keeping the wheels from locking by controlling skidding of the four wheels.
The ABS prevents the wheels from locking when braking. This function allows the vehicle to be steered under
braking and ensures vehicle stability under braking.
EBD (electronic braking distribution):
The electronic braking distribution unit optimises the brakeforce distribution between the front and rear axles. This
function ensures vehicle stability under braking.
Fault finding warning lights programming
Instrument panel warning light Meaning
- ABS ABS function inoperative.
Brake faults ABSElectronic braking regulation and ABS
function not working
Brake faults
flashing at 2HzABS flashing at 2HzABS computer is in fault finding mode.
- ABS flashing at 8HzTachometer index or vehicle
configuration not programmed.
ANTI-LOCK BRAKING SYSTEM
Fault finding – System operation
Page 8 of 57

38C-8V1 MR-376-X76-38C000$060.mif
38C
ABS BOSCH 8.1
Vdiag No.: 18
SETTINGS
VP001: Enter VIN.
This command permits manual entry of the vehicle's VIN into the computer.
Use this command each time the computer is replaced.
The VIN number (VF...) can be found on the manufacturer's plate on the door pillar and on the body panel
under the bonnet.
Programming procedure:
– connect the diagnostic tool,
– refer to the BOSCH 8.1 ABS fault finding,
– select parameter VP001,
– enter the VIN,
– clear the computer memory using command RZ001 Fault memory,
– exit fault finding mode,
– switch off the ignition,
– wait for the end of powerlatch,
– on the identification screen, using ID010 V.I.N. code, check that the code being entered has been
correctly recognised.
VP004: Vehicle parameters.
This command allows you to identify the vehicle on which the computer is installed.
Using PR063 Vehicle parameters, check that the parameters have been correctly recognised.
VP006: Enter last APV* operation date.
Whenever the ABS system is worked on in the shop, the date must be entered.
Select command VP006 on the diagnostic tool.
Enter the service date using the diagnostic tool keypad.
Using ID020 Read last After-Sales operation date, check that the date has been entered.
VP007: Tachometric index.
This command is used to program the computer memory with the index required to calculate vehicle speed
from the speed at which the tyres fitted on the vehicle turn.
Command VP007 is only used to stop the ABS warning light flashing after the computer has been
replaced.
Using PR030 Tachometric index, check that the index has been entered correctly.
APV*: After-SalesIMPORTANT:
The vehicle speed information is not delivered to the other computers by the ABS computer.
The vehicle speed signal is delivered by a speed sensor located on the gearbox.
ANTI-LOCK BRAKING SYSTEM
Fault finding – Programming
Page 49 of 57

38C-49
AFTER REPAIRClear the computer memory using command RZ001 Fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V1 MR-376-X76-38C000$170.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault Finding Chart38C
ABS BOSCH 8.1
Vdiag No.: 18
ALP3 Pull
NOTESOnly address this customer complaint after a complete check with the diagnostic
tool.
Disconnect one wheel speed sensor.
Start the engine and ensure that only the ABS fault warning light comes on. Do not drive the vehicle if the brake
fault warning light is also illuminated because the "braking compensator" function is no longer guaranteed.
Carry out a road test with the ABS thus out of order.
Is the fault still present under these conditions?
Raise the vehicle so that you can rotate the wheels and check:
– whether the speed sensors have been incorrectly
connected,
– whether the pipes on the hydraulic unit have been inverted.
For these two tests, consult and apply the procedures defined
in ALP2 Locking of one or several wheels.
Check the condition and conformity of the ABS targets.
If the fault is still present, contact the techline.If the brake pedal travel is relatively long,
bleed the brake circuit.
If the travel is normal, check the tyre
pressures, the front axle, or for any leaks in
the circuit.
NOYES
ABS8.1X76_V18_ALP3
Page 50 of 57

38C-50
AFTER REPAIRClear the computer memory using command RZ001 Fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V1 MR-376-X76-38C000$170.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault Finding Chart38C
ABS BOSCH 8.1
Vdiag No.: 18
ALP4 Drift
NOTESOnly address this customer complaint after a complete check with the diagnostic
tool.
Disconnect one wheel speed sensor.
Start the engine and ensure that only the ABS fault warning light comes on. Do not drive the vehicle if the brake
fault warning light is also illuminated because the "braking compensator" function is no longer guaranteed.
Carry out a road test with the ABS thus out of order.
Is the fault still present under these conditions?
Normal behaviour linked to the system operation during
the regulation phase, mainly on surfaces with uneven
grip or which are poorly laid.Road holding fault not related to the ABS.
Check the condition of the brake linings and that
they are to specification and check the tyre
pressures, the front axle, etc.
NOYES
ABS8.1X76_V18_ALP4
Page 51 of 57
38C-51
AFTER REPAIRClear the computer memory using command RZ001 Fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V1 MR-376-X76-38C000$170.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault Finding Chart38C
ABS BOSCH 8.1
Vdiag No.: 18
ALP5Unexpected ABS operation at low speed and slight pedal
pressure
NOTESOnly address this customer complaint after a complete check with the diagnostic
tool. Warning: ABS control is sensitive to poor traction (icy roads, wet cobblestones,
etc.).
It is possible to feel brake pedal vibrations which are associated with the reaction of the system in particular
circumstances, such as:
– crossing rumble strips,
– tight cornering with lifting of the inside rear wheel.
These vibrations may be linked to simple brake limiter activation, when the pressure on the rear axle is limited.
If the fault is different, check the speed sensor connectors (micro-breaks).
ABS8.1X76_V18_ALP5