Circuit Description
The electro-hydraulic power steering (EHPS) operates when voltage at the EHPS connector is in the range of 34-50 volts. The EHPS will go into standby mode if the supply voltage at the EHPS connector drops below 18 volts for more than 10 milliseconds. The EHPS module shall be turned back ON once the supply voltage rises above 22 volts, without a key cycle being required. If the supply voltage drops below 12 volts, the EHPS module drivers shall shut down and a key cycle will be required to reset. The EHPS module shall withstand voltages up to a transient voltage of 58 volts for 400 milliseconds. If the supply voltage exceeds 55 volts, the EHPS module drives shall shut down and a key cycle will be required to reset. The 36 volts power supply is grounded directly to the negative terminal of the EHPS.
When the electronic control unit (ECU) temperature exceeds 125°C (257°F), the powerpack will reduce the output of power assist. This will also reduce the output of the hydraulic pump. When the manifold temperature drops below 120°C (248°F), the powerpack will resume normal operation.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0485 Electric Hydraulic Steering Temperature Sensor Circuit
Conditions for Running the DTC
| • | The EHPS module is in RUN mode. |
| • | The ignition switch is in the ACC or ON position. |
| • | Battery voltage between 12-58 volts. |
Conditions for Setting the DTC
NOTE: This is a normal operation in extreme ambient conditions to protect the part.
| • | The EHPS module senses that the EHPS ECU temperature is greater than 125°C (257°F). |
| • | The steering wheel is held at lock indefinitely. |
Action Taken When the DTC Sets
| • | System operation is reduced. |
| • | The EHPS module operation is normal. |
| • | Stores DTC C0485 in the powertrain control module (PCM). |
| • | History DTC C0485 will be set in the PCM. |
Conditions for Clearing the DTC
| • | The ECU temperature falls below 120°C (248°F). |
| • | 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
| • | The ambient temperature is too high. |
| • | The steering pump is faulty. |
| • | The motor is faulty. |
| • | The steering fluid is low. |
| • | The hall effect sensors are faulty. |
| • | It may be necessary to check Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks to see if the ECU temperature is greater than 125°C (257°F).
-
This step checks for leaks in the hoses and fluid level.
-
This step checks for a blockage in the hoses.
Step | Action | Value(s) | 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 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Is the observed temperature greater than the specified value? | 125°C (257°F) | Go to Step 3 | Go to Diagnostic Aids | |
Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 4 | |
Check for a blockage in one of the steering pump hoses. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 5 | |
5 |
Important: Always perform the calibration procedure for the brake pedal position (BPP) sensor. Refer to Brake Pedal Position Sensor Calibration Description and Operation . Replace the electro-hydraulic power steering (EHPS) powerpack. Refer to Power Steering Pump Replacement . Did you complete the replacement? | -- | Go to Step 6 | -- |
6 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
