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Description And Operation

DESCRIPTION 

GC0183181Courtesy of CHRYSLER GROUP, LLC

The electric hydraulic power steering system is made up of the following components:

COMPONENT INDEX

1. Refer to ELECTRIC HYDRAULIC POWER STEERING (EHPS) PUMP .
2. Fluid Reservoir
3. Refer to BODY CONTROL MODULE (BCM) .
4. Steering Column
5. Refer to INSTRUMENT PANEL CLUSTER (IPC) .
6. Refer to STEERING COLUMN CONTROL MODULE (SCCM) .
7. Steering Wheel
8. Intermediate Shaft
9. Steering Gear
10. Steering Linkage
11. Fluid Lines
12. Steering Damper

OPERATION 

Multiple modules work together to improve vehicle steering assist at different rates at different speeds. At slow speeds, such as parking maneuvers, more assist is available and at high speeds less assist is available. The EHPS module uses the Controller Area Network-Chassis (CAN-C) and Controller Area Network-Interior High Speed (CAN-IHS) data bus for inputs and outputs of the information necessary for operation. The use of a scan tool is necessary for diagnostics. EHPS module faults are stored in a diagnostic program memory and are accessible with the scan tool. Faults remain in memory until cleared, or until after the vehicle is started approximately 50 times. Stored faults are not erased if the battery is disconnected.

The EHPS pump assembly contains a control module, brushless electric motor, and hydraulic pump integrated into a single unit. The EHPS pump draws power from the 12 volt electrical system and provides the necessary flow and pressure to the steering gear to provide normal power steering. The output flow of the EHPS pump is varied as a function of steering wheel rate and vehicle speed in order to provide the optimum flow of power steering fluid to the steering gear under all operating conditions. The EHPS pump will start to provide steering assist when the vehicle speed message showing greater than 5 km/h (3 mph) is received on CAN-C. If the vehicle speed message is missing at vehicle startup, the EHPS pump will not operate. If the vehicle speed message is lost during operation the EHPS pump will use a default vehicle speed of 85 km/h (59 mph) to calculate desired flow and as a result, steering effort will no longer be speed sensitive. If the steering wheel position message is lost the EHPS pump will use a default steering wheel rate of 230°/sec to calculate desired flow and as a result, steering effort may be higher on evasive steering maneuvers. The EHPS pump will resume normal operation automatically once any missing message or out of range condition noted above is restored to normal.

The EHPS warning lamp is used to visually indicate the fault/fail status of the EHPS system. The EHPS system is capable of controlling hydraulic output flow as a calibrated function of Engine Stop Start (ESS) status.

BODY CONTROL MODULE (BCM)

Refer to COMPONENT INDEX .

The BCM separates the branches of the bus networking systems, the BCM must act as a gateway module to allow communication between the different bus networks. The BCM will translate and share messages among all modules on the following bus networks. The BCM is the configuration master for the vehicle. As the configuration master, the BCM broadcasts configuration data over the bus whenever the ignition is in the RUN state.

CAN-C Inputs

CAN-IHS Outputs

ELECTRIC HYDRAULIC POWER STEERING (EHPS) PUMP

Refer to COMPONENT INDEX .

Power assist is provided by the EHPS pump mounted above the right front frame rail forward of the engine. The EHPS pump is an electrically operated hydraulic pump which supplies variable hydraulic fluid flow and pressure to the steering gear. The EHPS pump replaces the conventional belted power steering pump. The EHPS pump has an EHPS module attached (not replaceable separately). There are two electrical connectors on the EHPS pump assembly. One connector is a 12 volt low amperage module connector, and the other is a 12 volt higher amperage pump connector containing larger gauge wire for motor operation. The power steering hoses and steering gear are substantially unchanged in function from a conventional system. However, there are unique components for this system, such as hoses for routing and the gear for valve tuning.

The EHPS provides the following signals:

CAN-C Inputs

CAN-C Outputs

INSTRUMENT PANEL CLUSTER (IPC)

Refer to COMPONENT INDEX .

The IPC for this vehicle is located in the instrument panel above the steering column opening. The IPC gauges and indicators are visible through an opening in the cluster bezel and are protected by a clear plastic cluster lens that is secured to the cluster housing by integral latch formations. The instrument cluster assembly houses four analog gauges and has provisions for up to 25 international control and display symbol icon indicators that are all controlled by the IPC and standard on all models. The gauge graphics are white and gray against a black field except for a single red graduation at the high end of the gauge scale on both the engine temperature and fuel level gauges, and several red graduations at the high end of the gauge scale on the tachometer that designate the red line area, making them clearly visible within the instrument cluster in daylight. When illuminated by the cluster illumination lighting, the white and gray text and graphics as well as the red graphics still appear the same, the red gauge needles have internal optical illumination. Gauge illumination is provided by dimmer controlled Light Emitting Diode (LED) units soldered onto the IPC circuit board. The Gauge set and indicators shown above are an integrated part of the IPC, therefore are only serviced as a unit with the instrument cluster. The cluster lens and the cluster hood and mask unit are the only components of the instrument cluster assembly that can be serviced separately.

The IPC function for this system is to display a warning light for the EHPS system and receives the following signals:

CAN-C INPUTS

STEERING COLUMN CONTROL MODULE (SCCM)

Refer to COMPONENT INDEX .

The SCCM is located near the top of the steering column below the steering wheel. The SCCM includes the Steering Angle Sensor (SAS), the clockspring, the left (lighting) multifunction switch, and the right (wiper) multifunction switch.

The SCCM is secured to the steering column by an integral band clamp on the bottom of the instrument panel side of the SCCM. The SCCM has a centering attachment screw located on the top of the instrument panel side of the SCCM to be certain the SCCM is centered properly on the steering column.

The SCCM provides the EHPS system with the following signals:

CAN-C Inputs

CAN-C Outputs

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