Circuit Description
The electro-hydraulic power steering (EHPS) module communicates with the vehicle by means of the controller area network (CAN) data bus. The connector has 2 pins for CAN-high and 2 pins for CAN-low communications. No messages are received or sent on the class 2 data bus. The EHPS will read CAN messages from the powertrain control module (PCM), hybrid control module (HCM), and energy storage control module (ESCM). The PCM will act as the gateway to translate CAN messages into class 2 messages when required for diagnostic purposes.
The EHPS module receives the following messages from the CAN bus:
| • | Vehicle speed |
| • | Service disconnect status |
| • | PRNDL shift lever position |
| • | TCC/cruise dump signal |
The EHPS module sends the following message to the CAN bus:
| • | Brake pedal rate, position, in-range rationality, and out-of-range diagnosis |
| • | EHPS module status |
| • | Diagnostic messages to the driver information center (DIC) via PCM (EHPS module state: OK, Service Brake, Service Steer, fault) |
| • | Diagnostic information requested by service technicians via Tech 2 link (class 2 via PCM) |
| • | Steering wheel sensor diagnostic message (in-range, out-of-range failure) |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0550 Electroniic Control Unit (ECU) Performance
Conditions for Running the DTC
| • | The EHPS module is in RUN mode. |
| • | The ignition switch is in the ACC or ON position. |
| • | Battery voltage is between 12-58 volt. |
Conditions for Setting the DTC
The EHPS module detects internal errors.
Action Taken When the DTC Sets
| • | The SERVICE BRAKE SYSTEM and SERVICE STEER SYSTEM messages will be displayed. |
| • | A chime will sound. |
| • | The EHPS module operation is normal, but the electric motor control is inactive. |
| • | Stores DTC C0550 in the PCM. |
| • | History DTC C0550 will be set in the PCM. |
Conditions for Clearing the DTC
| • | After successful programming event |
| • | Using the scan tool |
| • | A history DTC will clear after 255 consecutive ignition cycles if the condition for the malfunction is no longer present. |
Diagnostic Aids
It may be necessary to check Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Power Steering Schematics Connector End Views Reference: Power Steering Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the scan tool display DTC C0550? | Go to Step 3 | Go to Diagnostic Aids | |
|
Important: Always perform the calibration procedure for the brake pedal position (BPP) sensor. Refer to Brake Pedal Position Sensor Calibration . Replace the electro-hydraulic power steering (EHPS) powerpack. Refer to Power Steering Pump Replacement . Did you complete the replacement? | System OK | -- | |
