GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The Body Control Module (BCM), or Electronic Suspension Control (ESC) Module, vehicles equipped with Real Time Damping (RTD), provides a pulse width modulated (PWM) supply circuit, and a control circuit to the Electronic Variable Orifice (EVO) solenoid. The supply circuit is used to regulate the current to the solenoid which controls the size of the power steering pump's output fluid orifice, depending on vehicle speed. This results in an increase or decrease in steering effort. The control circuit is used to disable the EVO outputs to provide full steering assist when a malfunction is detected.

NOTE: The BCM/ESC stores the DTCs scan tool data and special functions. However, the scan tool menu to access variable effort steering is located in chassis.

Conditions for Running the DTC

Vehicle speed greater than 8 km/h (5 mph).

EVO solenoid command greater than 5 percent PWM duty cycle.

Conditions for Setting the DTC

    • EVO output PWM less than 10 percent duty cycle and EVO output current greater than 260 ma.
    • EVO output PWM greater than 94 percent duty cycle and EVO output current less than or equal to 360 ma.

Action Taken When the DTC Sets

    • DTC C0495 will be stored in memory.
    • The EVO outputs will be disabled for the remainder of the ignition cycle.

Conditions for Clearing the MIL/DTC

    • A current DTC will clear on next ignition cycle with no malfunction present.
    • A history DTC will clear after 100 consecutive malfunction free ignition cycles.
    • Using the scan tool

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests the EVO solenoid circuits in there active state using the scan tool.

  2. Tests if the resistance of the EVO solenoid is within the specified range.

  3. Tests if the EVO solenoid supply circuit is shorted to voltage inside the control module.

  4. Tests if the EVO solenoid supply circuit is shorted to voltage

  5. Program the BCM/ESC Module after replacement.

Step

Action

Value(s)

Yes

No

Schematic Reference: Steering Assist Schematics

1

Important:: If DTC C0501 is also set, perform the diagnostic procedure for C0501 before proceeding.

Did you perform the Variable Effort Steering Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Variable Effort Steering .

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the EVO solenoid ON and OFF.

Does the EVO solenoid turn ON and OFF with each command?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the EVO solenoid harness connector.
  3. Measure the resistance of the EVO solenoid.

Does the resistance measure within the specified value?

11-13 ohms

Go to Step 4

Go to Step 8

4

Inspect for poor connections at the EVO solenoid harness connector.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 5

5

  1. Probe the EVO solenoid supply circuit at the solenoid harness connector with a test lamp connected to ground.
  2. Turn ON the ignition, with the engine OFF.

Does the test lamp turn on when the ignition is turned ON?

--

Go to Step 9

Go to Step 6

6

Does the test lamp remain on continuously with the ignition ON or OFF?

--

Go to Step 7

Go to Step 10

7

Test the EVO solenoid supply circuit for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 9

8

Replace the EVO solenoid. Refer to Power Steering Solenoid Actuator and Discharge Fitting Replacement .

Did you complete the replacement?

--

Go to Step 10

--

9

Replace the BCM/ESC module. Refer to Body Control Module Replacement in Body Control Systems, or Electronic Suspension Control Module Replacement in Real Time Damping.

Did you complete the replacement?

--

Go to Step 10

--

10

  1. Use the scan tool in order to clear the DTCs .
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK