Page 88 of 101

38C-88
AFTER REPAIRClear the computer fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V3 MR-413-X44-38C050$180.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault finding chart38C
Bosch 8.1 ESP
Vdiag No.: 05
ALP2 Locking or braking of one or more wheels
NOTESOnly consult this customer complaint after a full check with the diagnostic tool.
Check the conformity of the mechanical components (see MR 411, Mechanical,
30A, General information, Brake, Specifications).
REMINDERLocking of wheels on a vehicle fitted with ABS or squealing of the tyres, which feels like
locking to the customer, may be linked to normal operation of the system and should not
always be considered a fault.
Braking with ABS regulation on very poor roads can cause significant squealing.
However, if the wheel(s) is/are actually locking, lift the vehicle in order to be able to rotate the wheels and check:
Possible inversion when connecting the speed sensors.
Use parameters PR001 Front right-hand wheel speed, PR002 Front left-hand wheel speed, PR003 Rear right-
hand wheel speed and PR004 Rear left-hand wheel speed whilst slowly turning the wheels in question and
checking the consistency of the results obtained.
If the value measured is zero, rotate the other wheels to confirm an electrical inversion of the sensors and repair
the wiring harness.
If a single reading is incorrect:
–Check that the sensor casing is secured when rotating.
–Check that the wheel speed sensor mounting is in good condition.
–If that is unsuccessful, replace the corresponding sensor and repeat the check procedure (see MR 411
Mechanical, 38C, Anti-lock braking system, Wheel speed sensor: Removal - Refitting).
–A possible inversion of the pipes on the hydraulic unit (see MR 411, Mechanical, 38C, Anti-lock braking
system, Hydraulic braking unit, List and location of components).
Run commands AC003 Front left-hand wheel solenoid valves, AC004 Front right-hand wheel solenoid
valves, AC005 Rear left-hand wheel solenoid valves and AC006 Rear right-hand wheel solenoid valves while
depressing the brake pedal and check for locking/unlocking cycles on the wheel concerned (see Dealing with
command modes).
If the cycles are not detected on the wheel tested (wheel remains locked), check if they occur on another wheel
(confirmation of a reversal after a repair, see MR 411, Mechanical, 38C, Hydraulic braking unit, List and
location of components).
If the cycles are not detected on a wheel and the pipes have not been inverted, replace component 1094
(see MR 411, Mechanical, 38C, Hydraulic braking unit, Removal- Refitting).
Check that the sensor holder does not rotate (depending on fitting).
Check the quality of the mounting of the wheel speed sensors (correct clipping for the front wheels).
Check the conformity of the targets: the condition and the number of teeth= 48 (using the command SC001
"Check target teeth").
Replace if necessary.
If the fault is still present after these checks, replace component 1094 (see MR 411, Mechanical, 38C, Hydraulic
braking unit, Removal- Refitting).
ESP_V05_ALP2
Page 89 of 101

38C-89
AFTER REPAIRClear the computer fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V3 MR-413-X44-38C050$180.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault finding chart38C
Bosch 8.1 ESP
Vdiag No.: 05
ALP3 Pull
NOTESOnly consult this customer complaint after a full check with the diagnostic tool.
Check the conformity of the mechanical components (see MR 411, Mechanical,
30A, General information, Brake, Specifications).
Disconnect one wheel speed sensor.
Start the engine and check that only the ABS
and ESP fault warning lights are lit.
Is the brake fault warning light also lit?Do not drive, the "braking compensator" function
cannot be carried out (risk of a spin).
Deal first with the faults using the diagnostic tool.
Drive the vehicle and operate the brakes.
Is the customer complaint still present
under these conditions?If the brake pedal travel is comparatively long, bleed
the brake circuit (see MR 411, Mechanical, 30A,
General information, Brake circuit, Bleeding).
If the travel is normal, check that the 4 vehicle tyres
are identical and in accordance with the
manufacturer's recommendations (see MR 411,
Mechanical, 35A, Wheels and tyres, Tyre, Tyre
pressure, Identification and Tyre, Identification).
Check and adjust the wheel alignment (see MR 411,
Mechanical, 30A, General information, Front
axle, Adjustment).
Check for any leaks on the brake circuit.
Apply the fault finding procedure described in the ALP 2
"Locking of one or several wheels".
YES
NO
YES
NO
ESP_V05_ALP3
Page 90 of 101

38C-90
AFTER REPAIRClear the computer fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V3 MR-413-X44-38C050$180.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault finding chart38C
Bosch 8.1 ESP
Vdiag No.: 05
ALP4 Drift
NOTESOnly address this customer complaint after a complete check with the diagnostic tool.
Disconnect one wheel speed sensor.
Start the engine and check that only the ABS
and ESP fault warning lights are lit.
Is the brake fault warning light also lit?Do not drive, the "braking compensator" function
cannot be carried out (risk of a spin).
Deal first with the faults using the diagnostic tool.
Drive the vehicle and operate the brakes.
Is the customer complaint still present
under these conditions?It is a road holding fault not related to the ABS/ESP
system.
Check the condition and conformity of the front and
rear brake linings.
Check that the 4 vehicle tyres are identical and in
accordance with the manufacturer's
recommendations (see MR 411, Mechanical, 35A,
Wheels and tyres, Tyre pressure, Identification
and Tyres, Identification).
Check that the pressures of the 4 tyres conform to
the manufacturer's recommendations (see MR 411,
Mechanical, 35A, Wheels and tyres, Tyre
pressure, Identification).
Check and adjust the wheel alignment (see MR 411,
Mechanical, 30A, General information, Front
axle, Adjustment).
Normal behaviour linked to the system operation during the
regulation phase, mainly on surfaces with uneven grip or
which are poorly laid.
YES
NO
YES
NO
ESP_V05_ALP4
Page 91 of 101

38C-91
AFTER REPAIRClear the computer fault memory.
Carry out a road test followed by another check with the diagnostic tool.
V3 MR-413-X44-38C050$180.mif
ANTI-LOCK BRAKING SYSTEM
Fault finding – Fault finding chart38C
Bosch 8.1 ESP
Vdiag No.: 05
ALP5Unexpected ABS operation at low speed and with slight pedal
pressure
NOTESOnly address this customer complaint after a complete check with the diagnostic tool.
Important: ABS regulation is sensitive on slippery surfaces (ice, wet cobbled
streets, etc.).
Brake pedal vibrations associated with the reactions of the system may be felt in
particular circumstances, such as:
–Crossing speed bumps.
–Tight cornering with lifting of the inside rear wheel.
These vibrations also may be linked merely to activation of the Braking distributor
function, when the pressure on the rear axle is limited.
Check the conformity of the mechanical components (see MR 411, Mechanical,
30A, General information, Brake, Specifications).
If the fault is not one of the situations indicated above, check the correct connection of the wheel speed sensors,
the air gap between these sensors and the magnetic targets.
Refer to the interpretation of fault DF063 Wheel speed consistency.
ESP_V05_ALP5
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