Teach-in electronic-hydraulic auxiliary steering (EHZ)

AR46.80-W-1110A

Teach-in electronic-hydraulic auxiliary steering (EHZ)

04.08.2017

Model

950.203/204/205 with rear axle 749.109

with code AN9 (Hydraulically steered trailing axle)

Modification notes

06.07.2017

Work procedure completely revised.

1

Adapter (A 000 540 14 74)

X119

EHZ diagnostic socket

2

Test connection

3

Pressure limiting valve

4

Screw

 Danger

Risk of death caused by vehicle slipping or toppling off during lifting

Only lift vehicle at the lift support points specified by the vehicle manufacturer.

AS00.00-Z-0032-01A

 Warning

Risk of accident from vehicle starting off by itself when engine running. Risk of injury (bruises and burns) resulting from working on the engine while it is being started or when it is running.

Secure vehicle to prevent it from starting off by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.

AS00.00-Z-0005-01A

 Warning

Risk of injury from being trapped in the swivel range of steered axles

Ensure that no persons or objects are in the swivel range of all steered axles when turning the steering wheel. Do not stand in the swivel range of the additional steering axle when the engine is running.

AS46.00-Z-0002-01A

Topical note

Special instructions for lifting and supporting vehicle

AH00.60-N-0100-01B

Program

1

Read out fault memory with the aid of the flash code

 When the teach-in process starts, all the faults stored in the fault memory of the electrohydraulic auxiliary steering (EHZ) control unit are deleted.

2

Check the tires on the front axle

If the tires indicate that the toe setting is incorrectly set.



Check toe at front axle and adjust if necessary.

AR40.20-W-0323A

3

Check the tires on the steered additional axle

If the tires indicate that the toe setting is incorrectly set.



Check toe on steered additional axle and adjust, if necessary.

AR40.20-W-0600A

4

Check center steering position and adjust, if necessary

Only if this was not checked or adjusted already when checking the straight-ahead position or the toe.

AR46.20-W-3020A

 When the front axle is in the straight-ahead position, the steered additional axle and its steering cylinders must also be in the center position.
Remove the wheel alignment measurement system components after the checking or adjusting operations.
Leave the turn plates, alignment bridges and the brake pedal jack on the vehicle.

5

Connect adapter (1) to the EHZ diagnostic socket (X119)



AD46.80-W-2001-03A

 The adapter (1) is available under the part number A 000 540 14 74.

6

Switch on ignition

7

Switch off centering of electrohydraulic auxiliary steering

 The electrohydraulic auxiliary steering must be actively engaged. The indicator lamp in the axle centering switch (S139) may not light up.

8

Slacken lock nut for bolt (4) on pressure limiting valve (3) and unscrew bolt as far as the stop

 Leave the bolt open for at least 15 seconds. The pressure in the centering circuit is now reduced.

9

Insert one side of the hose into a suitable container, and connect the other side to the test connection (2)

 The pressure in the centering circuit is now completely dissipated.

 Hose

*400589019100

10

Screw in the bolt (4) up to the end stop and tighten the counternut

11

Disconnect hose from test connection (2)

12

Switch off ignition

 Leave ignition switched off for at least 10 seconds.

13

Switch on ignition

 The indicator lamp of the electrohydraulic auxiliary steering lights up permanently. The electrohydraulic auxiliary steering (EHZ) control unit now checks the internal and external power supply, as well as the valve connections. If the test is passed, the indicator lamp goes out.

14

Start the engine and run at a speed between 1000 and 1400 rpm

 The indicator lamp of the electrohydraulic auxiliary steering lights up permanently.
The centering circuit is automatically filled for approx. 20 seconds (filling noise audible at valve unit).
The valves in the steering circuit are also checked here.

15

Move the steering gear within a period of 10 seconds after completing the test procedures, to the center position

Vehicles with steering gear 765.82, 765.889

AR46.20-W-0500-01A

 The indicator lamp still lights up permanently.

16

Leave front axle for at least 6 seconds in the center position

 The value of the center position is recorded here by the electrohydraulic auxiliary steering (EHZ) control unit. The indicator lamp of the electrohydraulic auxiliary steering flashes. Initialization of the steering angle sensors commences.

17

Turn steering wheel to left up to end stop and hold there for approx. 6 seconds

18

Turn steering wheel to right up to end stop and hold there for approx. 6 seconds

19

Repeat operation steps 17 and 18, then move the steering into the center position and leave it there

 The remaining procedures are automatically conducted by the electrohydraulic auxiliary steering (EHZ) control unit.
If all the preceding operations are OK, the flash frequency of the indicator lamp increases.

20

Check if the wheels on the steered additional axle are automatically turned in all the way total of 4-times

 On vehicles with a steered trailing axle, the wheels are turned first all the way to the right, then the left, then to the right again and finally to the left.
On vehicles with a steered leading axle, the wheels are turned first all the way to the left, then the right, then to the left again and finally to the right.

21

Check if the steered additional axle is automatically steered back to the center position

 The electrohydraulic auxiliary steering (EHZ) control unit automatically runs a function test (the centering circuit is filled again, the correction factors for both steering angle sensors calculated, etc.).

22

Check EHZ indicator lamp

 The initialization process is complete when the EHZ indicator lamp goes out.

If the indicator lamp flashes at an interval of 5 seconds once or several times.



Determine the reason for the fault.



Electronic-hydraulic auxiliary steering (EHZ) diagnosis diagnostic fault code memory

AD46.80-W-4001B

23

Stop engine and switch off ignition

24

Detach the adapter (1) from the EHZ diagnostic socket (X119)

25

Remove all turn plates and alignment bridges as well as the brake pedal jack

26

Perform a test drive

 During the road test check the overall steering behavior of the vehicle.