38C-67
MR-413-X44-38C000$940_eng.mif
V1
ANTI-LOCK BRAKING SYSTEM
Fault finding - Fault Finding Chart
MK70 ABS
Vdiag No: 04
38C
ALP 2 Locking of one or more wheels
NOTESOnly consult this customer complaint after a complete check with the diagnostic tool.
Check the conformity of the mechanical components.
NOTESLocking 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:
–Locking is allowed below 4 mph (6 km/h) (system regulation will not be activated).
–Braking with ABS system regulation on very poor roads (significant grating).
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.
Using parameters PR001, PR002, PR003 and PR004, rotate the wheels slowly and check 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.
–Possible inversion of pipes on the hydraulic unit.
Use commands Front left wheel solenoid valves, Front right wheel solenoid valves, Rear left wheel solenoid
valves and Rear right wheel solenoid valves while depressing the brake pedal and check for 10 unlocking/locking
cycles on the wheel concerned (see Dealing with command modes). If the 10 cycles are not carried out on the
wheel tested (wheel remains locked), check whether they are carried out on another wheel (confirmation of a
reversal: repair).
If the 10 cycles are not detected on a wheel and the pipes have not been reversed, change the hydraulic unit.
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: condition, number of teeth = 48 (using command SC001 Check target
teeth).
If the fault is still present after these checks, replace the hydraulic unit.
AFTER REPAIRClear the computer fault memory.
Carry out a road test followed by another check with the diagnostic tool.
ABS_V04_ALP2
