Fault location tree

ALP 1

No communication with the ABS ECU

INSTRUCTIONS

Without.

Make sure the diagnostic tool is not the cause of the fault by trying to communicate with an ECU on another vehicle. If the tool is not the cause and communication cannot be established with any other ECU on the same vehicle, a faulty ECU may be disturbing the multiplexed network. Check the battery voltage and carry out the necessary work to obtain a compliant voltage (9.5 volts < compliant battery voltage < 17.5 volts).

Carry out a multiplexed network diagnosis using the diagnostic tool.

Check the presence and condition of the ABS fuses in the passenger compartment fuse panel and in the engine fuse box. Check the ECU connector connection and the condition of its terminals. Check the ABS earths (quality, corrosion, tightness of the earth screw above the ABS unit). Check that the ECU is correctly supplied: Earth on pins 1 and 4 of the 46-pin connector. + AVC on pins 2 and 3 of the 46-pin connector. + APC on pin 18 of the 46-pin connector.

Check that the diagnostic socket is correctly supplied: + AVC on pin 16. + Ignition feed on pin 1. Earth on pin 5.

If communication still cannot be established after these checks, contact your Techline.

AFTER REPAIR

Clear the ECU memory.

Carry out a road test followed by a further check with the diagnostic tool.

ALP 2

Locking of one or more wheels

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Reminder: Wheel locking on a vehicle fitted with ABS, or tyre squeal which the customer perceives as locking, may be a normal system response and must not automatically be treated as faults: Braking with ABS regulation on very poor road surfaces (loud squealing).

If a wheel really is locking, raise the vehicle so the wheels can be turned, and check: A possible reversal in the wiring of the speed sensors. Use parameters PR001, PR002, PR003 and PR004 while slowly turning the associated wheels, and make sure the results are consistent. If the measured value is zero, turn the other wheels to confirm an electrical reversal of the sensors, and repair the wiring. A possible reversal of the piping at the hydraulic unit. Use commands AC003 "Front left wheel solenoid valves", AC004 "Front right wheel solenoid valves", AC005 "Rear left wheel solenoid valves" and AC006 "Rear right wheel solenoid valves" while pressing the brake pedal, and check for five release/lock cycles on the wheel concerned (see the chapter "Control mode processing"). If the five cycles are not performed on the wheel tested (wheel held locked), check whether they are performed on another wheel (to confirm a crossed pipe connection). If the five cycles are not performed on a wheel with no crossed pipes, replace the hydraulic unit.

Check that the sensor holder is firmly retained and does not rotate. Check that the wheel speed sensor is securely fitted (clip-in). Check that the tone wheels conform using the specific command SC001 "tone wheel tooth check": condition, number of teeth = 48. If the fault persists after these checks, contact your Techline.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 3

Pulling

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 4

Snaking

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 5

Unexpected ABS operation at low speed and light pedal effort

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Warning: ABS control is "sensitive" on very low grip surfaces (ice, wet tiles, ...).

Vibrations may be felt through the brake pedal, linked to the system's response, in the following particular situations:

• Driving over speed bumps.
• Tight bend with inside rear wheel lifted.

This feeling may be caused simply by the "brake force distribution" function becoming active when rear axle pressure is limited.

If the problem is different, check the speed sensor connectors (micro-breaks) and the air gaps.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 6

Unexpected ABS operation on poor road surfaces

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

On rough roads, it is normal to feel jolts and vibrations through the pedal, as well as more pronounced squealing than on good road surfaces.

This results in an impression of variable braking efficiency, which is to be considered normal.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 7

Unexpected ABS operation when using special equipment (radio telephone, CB, ...)

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Check that the equipment causing the problem is approved for use.

Check that this equipment has been correctly installed without modifying the original wiring, particularly that of the ABS (connections to earth, + APC and - AVC of the ABS are not permitted).

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 8

Increase in brake pedal travel following a control phase (with a leaking pedal when control begins)

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Air passing from the hydraulic unit regulation channels into the brake circuits. Bleed the circuits following the procedure recommended in the Repair Manual (using diagnostic tool command modes). After the work, carry out a road test with ABS regulation.

If the fault persists, repeat the previous operation 1 or 2 more times. If the customer complaint is particularly pronounced and bleeding does not improve it, contact your Techline.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 9

Long pedal

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Air in the brake circuits.

Carry out a conventional bleed of the circuits, starting with the right rear brake, then left rear, left front, and finally right front. Repeat the operation if necessary.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 10

Brake pedal vibration

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Normal brake pedal feedback during an ABS control phase or rear axle pressure limitation ("electronic brake force distribution" function).

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 11

Noise from pump, pipes or hydraulic unit

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

• Unit vibration: check the presence and condition of the insulating bushes on the unit mounting bracket.
• Pipe vibration: check that all pipes are correctly clipped into their retaining clips and that there is no contact between pipes, nor between pipes and bodywork.

To determine where the noise is coming from, use the actuation commands for the solenoid valves "Front left wheel solenoid valves", "Front right wheel solenoid valves", "Rear left wheel solenoid valves" and "Rear right wheel solenoid valves" while pressing the brake pedal.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 12

Unwanted ESP intervention

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

• Make sure that all four tyres on the vehicle are identical.
• Using the diagnostic tool, make sure that configuration reading LC003 "VEHICLE PARAMETERS" matches the vehicle definition exactly.
• If necessary, use command VP004 "VEHICLE PARAMETERS" with the diagnostic tool to set the variant appropriate to the vehicle type.
• Check the condition and correct connection of the combined sensor connector.
• Make sure the combined sensor is securely fitted and correctly oriented on the body shell.
• Perform the steering wheel angle calibration in the "Electronic power steering" area using the diagnostic tool.
• Clear the ABS-ESP computer memory, carry out a road test, then a further check with the diagnostic tool.
• If the fault persists, carry out a wheel alignment check. Adjust if necessary, then perform a new steering wheel angle calibration in the "Electronic power steering" area using the diagnostic tool.
• If the fault persists, contact your Techline

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.

ALP 13

Brake light illumination fault

INSTRUCTIONS

Only refer to this customer complaint after a complete check with the diagnostic tool.

Using the diagnostic tool, check that ET017 operates correctly. Otherwise, apply the diagnostic procedure associated with ET017 described in the previous pages.

If the lights still do not work, check the operation of the ignition relay. The relay is closed at rest (check continuity between pins 3 and 4 of the relay). Replace the relay if necessary. Ensure continuity of the link between pin 1 of the brake switch and pin 4 of the relay holder. Repair if necessary.

AFTER REPAIR

Carry out a road test, then a check with the diagnostic tool.