Land Rover Discovery: Vehicle Dynamic Suspension
- Operation
The SUM uses a combination of information from other system modules and
data from the height sensors to measure the vehicle and suspension states
and driver inputs. Using this information, the SUM applies algorithms to
control the shock absorbers for the current driving conditions.
The SUM receives the following signals on the high speed CAN Chassis bus
from the stated system components:
- Brake pressure - Anti-lock Brake System (ABS) control module.
- Brake pressure quality factor - ABS control module.
- Car configuration parameters - Central Junction Box (CJB).
- Engine speed - Engine Control Module (ECM).
- Engine speed quality factor - ECM.
- Engine torque flywheel actual - ECM.
- Engine torque flywheel actual quality factor - ECM.
- Gear position target - Transmission Control Module (TCM) - automatic
transmission vehicles only.
- Lateral acceleration - ABS control module.
- Power mode (ignition signal) - CJB.
- Power mode quality factor - CJB.
- Roll stability control mode - ABS control module.
- Steering wheel angle - ABS control module.
- Steering wheel angle speed - ABS control module.
- Steering wheel angle status - ABS control module.
- Terrain mode requested - Terrain Response (TR) switchpack - automatic
transmission vehicles only.
- Torque converter slip - TCM - automatic transmission vehicles only.
- Vehicle information parameters HS - CJB.
- Vehicle speed - ABS control module.
- Vehicle speed quality factor - ABS control module.
- Front left wheel speed - ABS control module.
- Front left wheel speed quality factor - ABS control module.
- Front right wheel speed - ABS control module.
- Front right wheel speed quality factor - ABS control module.
- Rear left wheel speed - ABS control module.
- Rear left wheel speed quality factor - ABS control module.
- Rear right wheel speed - ABS control module.
- Rear right wheel speed quality factor - ABS control module.
The SUM also outputs information on the high speed CAN Chassis bus for use by
other systems as follows:
- Fault message - Instrument Cluster (IC).
- Terrain mode change status - TR switchpack - automatic transmission
vehicles only.
- Terrain mode - TR switchpack - automatic transmission vehicles only.
The SUM monitors the input signals and operates the shock absorber
solenoids. The input signals are used in control functions and a force
required for each shock absorber, for each function, is calculated. An
arbitrator monitors the force requirements from each function and
apportions a force to a shock absorber. The force is converted to the
appropriate current and sent to the shock absorber.
The control functions are as follows:
- Body Control - Uses suspension height sensors and CAN bus inputs.
Calculates road induced body motions 200 times a second and sets each
shock absorber to the appropriate level to maintain a flat and level body
attitude. Provides improved body control without loss of ride quality.
Roll Rate Control - Uses CAN inputs. Predicts vehicle roll rate due to
driver steering inputs 100 times a second and increases damping to
reduce roll rate. Provides improved control and driver confidence.
- Pitch Rate Control - Uses CAN inputs. Predicts vehicle pitch rate due to
driver throttle and braking inputs 100 times a second and increases
damping to reduce pitch rate. Provides improved control and driver
confidence.
- Bump Rebound Control - Uses suspension height sensor and CAN inputs.
Monitors the position of the wheel 1000 times a second and increases the
damping rate as the shock absorber approaches the end of its travel.
Provides improved ride quality.
- Wheel Control - Uses suspension height sensor and CAN inputs. Monitors
the position of the wheel 1000 times a second and provides the appropriate
level of damping for the suspension velocity.
- Dynamic program - Uses suspension height sensor and CAN inputs. The
Dynamic program uses a completely separate tune from the normal
control, an alternative set-up for the body, wheel, roll rate, pitch rate
and
bump/rebound control to give a tighter, sportier driving feel.
- Off-road modification - Uses suspension height sensors and CAN inputs.
Evaluates the road surface roughness and appropriately adapts the level
of damping control demanded from the various functions: body, wheel,
roll rate, pitch rate and bump/rebound control.
Under normal road conditions, when the vehicle is stationary with the
engine running, the dampers are set to the lowest damping condition to
reduce power consumption.
The SUM has a constant power supply, and an ignition power feed from the
Rear Junction Box (RJB). The ignition power feed relay is energized by the
CJB. The relay remains energized for a period of time after the ignition is
off. This allows the SUM to record and store any Diagnostic Trouble Code
(DTC) relating to adaptive damping system faults.
CONTROL DIAGRAM
NOTE: A = Hardwired; AL = Pulse Width Modulation (PWM); AM = High
speed - Controller Area Network (CAN) Chassis bus; AN = High speed
CAN Powertrain bus.
- Suspension Control Module (SUM)
- Engine Control Module (ECM)
- Instrument Cluster (IC)
- Transmission Control module (TCM)
- Transmission Control Switch (TCS)
- Central Junction Box (CJB)
- Rear Differential Control Module (RDCM)
- Anti-lock Brake System (ABS) control module
- Power Steering Control Module (PSCM)
- Terrain Response (TR) switchpack
- Gateway Module (GWM)
- Adaptive shock absorber (4 off)
- Ground wire
- Power supply
- Height sensor (4 off)
Vehicle dynamic suspension diagnosis and testing
PRINCIPLES OF OPERATION
For a detailed description of the Vehicle Dynamic Suspension, refer to the
relevant Description and Operation section in the workshop manual. REFER
to: Vehicle Dynamic Suspension (204-05 Vehicle Dynamic Suspension,
Description and Operation).
INSPECTION AND VERIFICATION
CAUTION:
Diagnosis by substitution from a donor vehicle is NOT acceptable.
Substitution of control modules does not guarantee confirmation of a
fault, and may also cause additional faults in the vehicle being tested
and/or the donor vehicle.
NOTES:
- Verify the customer concern
- Visually inspect for obvious signs of damage and system integrity
Visual Inspection
- If an obvious cause for an observed or reported concern is found,
correct the cause (if possible) before proceeding to the next step
- If the cause is not visually evident, verify the symptom and refer to
the
Symptom Chart, alternatively check for Diagnostic Trouble Codes
(DTCs) and refer to the DTC Index
- Check DDW for open campaigns. Refer to the corresponding bulletins
and SSMs which may be valid for the specific customer complaint and
carry out the recommendations as required
DTC INDEX
For a list of Diagnostic Trouble Codes (DTCs) that could be logged on this
vehicle, please refer to Section 100-00. REFER to: Diagnostic Trouble Code
Index - DTC: Suspension Control Module (SUM) (100-00 General
Information, Description and Operation).
READ NEXT:
Overview
COMPONENT LOCATION
NOTE:
Only vehicles fitted with a full-size spare wheel are equipped with a
tire pressure sensor in the spare wheel.
TIRE PRESSURE MONITORING SYSTEM (TPMS)
Instrument C
TIRE LOCATION
Because of the requirement for different pressure targets and thresholds for
the front and rear tires, the Tire Pressure Monitoring System (TPMS) can
identify the location of the tires o
SEE MORE:
COMPONENT LOCATION - VEHICLES WITH ACTIVE DRIVELINE
NOTE:
Automatic transmission shown, manual transmission similar
Power Transfer Unit (PTU)
Driveshaft
Rear Drive Unit (RDU)
Hydraulic lines
OVERVIEW
Vehicles with Active Driveline connect to the transmission in the same way
as vehicles witho
All vehicles
WARNING:
Always chock the front wheels when jacking the rear of the vehicle.
Apply the parking brake.
Select 'P' - Park on automatic transmission selector.
Select 'N' - Neutral on manual transmission.
Vehicles with four-wheel drive
On vehicles with four-wheel drive, position lifting