EAS - Re-Calibration Criteria
NO. 06/02/94/USDATE: 07/01/94
MODEL
Range Rover
AFFECTED VEHICLES
All Electronic Air Suspension Derivatives
SUBJECT
Electronic Air Suspension - Re-Calibration
DETAIL
Analysis of warranty statistics has shown a rapid rise in Electronic Air Suspension re-calibration without necessarily changing any associated components in the system. Land Rover Engineers have identified that unnecessary re-calibration may well be being carried out without fully understanding the need for undertaking this process.
This bulletin explains the criteria for recalibration, why a calibration may fail and reinforces the proper calibration procedures.
ACTION REQUIRED
When vehicle trim heights appear to be away from specification the procedure listed must be precisely followed.
PARTS INFORMATION
Not applicable.
PROCEDURE
Reference should also be made to Technical Bulletin P93/68-001.
1. WHEN IS CALIBRATION REQUIRED.
Calibration is only required when either a height sensor or the Electronic Control Unit (ECU) is replaced.
Calibration CANNOT/DOES NOT drift out of tolerance electronically but can be affected by a faulty height sensor as outlined in Bulletin P93/68-001, a damaged height sensor linkage or tire wear as outlined in the attached Procedure for Checking Vehicle Lean on Electronic Air Suspension Vehicles (for which an allowance should be made - see item 2.)
2. WHY THE CALIBRATION PROCEDURE LISTED MUST BE USED.
a. The vehicle must be parked on a smooth level surface with wheels straight ahead to ensure that the vehicle can achieve as level an attitude as possible.
b. Tire pressures should be correct and the vehicle unladen as these two items will affect tire profile height.
c. Items 5 to 11 are essential to establish if a vehicle requires calibration.
Important Note
The wheel arch heights MUST NOT be measured with the engine off as in this condition the Air Suspension system does not level to the same accuracy and will be outside the target height of 790 +/- 7 mm specification. Additionally all doors must be shut to allow the system to level the vehicle to the target heights.
d. Item 11 refers to the effect of tire wear. Tread depth on new tires is 11 mm. If a vehicle has tires that have worn ie: 4 mm of remaining tread depth, an allowance of 7 mm should be made. For example:
Measured height to wheel arch = 780 mm
Tread depth allowance 11 - 4 = 7 mm
Effective trim height 780 + 7 = 787 mm
THE VEHICLE SHOULD NOT BE CALIBRATED IN THIS CASE.
e. When a calibration is carried out care must be taken to ensure that Millimeters and NOT Centimeters are used. If centimeters are used the vehicle will adopt a "Rear Up, Front Down" attitude and fail calibration.
3. WHY A CALIBRATION MAY FAIL
a. Centimeters used instead of Millimeters. Trim heights should always be in the region of 700 - 900 mm.
b. The system is not up to pressure when calibration is commenced.
c. If a calibration procedure is aborted half way through, default heights will remain in the ECU, which may be out of specification. It is therefore important that the whole calibration procedure is completed.
d. If a calibration has been completed, and when "access" height is selected the down warning light continues to flash, the following procedure must be carried out:
i. Remove both rear bump stops.
ii. Calibrate using the procedure attached.
iii. Refit the rear bump stops.
The vehicle should now achieve "access" height with the down warning light permanently illuminated.
The cause of a vehicle not achieving the default "access" height at the rear is attributable to a build up of tolerances resulting in bump stop intrusion. With the bump stops removed it allows the vehicle to reach the ECU default demand height which ultimately allows correct calibration to be achieved.
Procedure for Checking Vehicle Lean on Electronic Air Suspension Vehicle.
1. Park vehicle on a smooth, and level surface with the front wheels in the straight ahead position.
2. Check that the tire pressures conform to specification. If non standard wheels and/or tires are fitted these will affect the calibration.
NOTE
For calibration purposes it is strongly recommended that standard wheels and tires are fitted.
3. Unload the vehicle if applicable.
4. If a new ECU or height sensor has been fitted, connect the hand held tester and proceed to No. 12.
5. Connect the hand held tester and select "Dynamic tests", then start the engine.
6. With all the doors closed allow the vehicle to level to standard height - this may take up to 4 minutes in cases of low reservoir pressure. Leave the engine running.
7. Examine the "Target height" on the hand held tester screen. Where either of the following value tables in standard height are seen, an uncalibrated ECU is fitted. Note which table is present and proceed to No. 12.
NOTE
Hand held tester Table 1 layout.
FL-104-FR-104
RL-111-RR-111
Hand held tester Table 2 Layout
FL-122-FR-122
RL-110-RR-110
Procedure for Checking Vehicle Lean on Electronic Air Suspension Vehicle.
8. Compare the "Actual height" with the "Target height". The actual height should be within +/- 1 of the target height. Note however that at the front of the vehicle it is the average value for left and right that should be considered (where this results in a half, the figure should be rounded down). Record both target and actual values, as given by the hand held tester.
Example:
Target height in standard
FL-111-FR-112
RL-114-RR-116
Therefore average front target = 111 1/2
Rounded down, target = 111.
Actual height in standard.
FL-109-FR-113
RL-115-RR-115
Therefore average front actual = 111
Comparing the average front valve- the two match exactly.
Comparing the individual rear valve- the actual are both within +/- 1 of the targets. This indicates that the system is able to perform proper height control.
9. Measure and record the wheel arch heights in mm, taking care to measure vertically through the wheel center.
10. If the vehicle has been unable to achieve a match between actual and target heights (as described in no 8) do not recalibrate. Investigate possible causes e.g. lack of air in reservoir, stuck corner valve, trapped air pipe etc.
11. If the vehicle wheel arch heights are 790 mm +/- 7 mm (note: take the average at the front) then the vehicle is to specification - do not recalibrate.
NOTE
If the tires are badly worn, the wheel arch heights will tend to be low.
12. Select calibration procedure on hand held tester.
13. Proceed as directed by hand held tester instructions, taking care to measure accurately.
IN ALL CASES:
Complete a product report detailing the symptoms and any measurements in full, and send it to Land Rover North America Technical Support.
WARRANTY
Normal warranty policy and procedure applies.
COMP. CODE
6R0A
SRO