GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Yukon XL - 2WD 🢒 Steering 🢒 Variable Effort Steering 🢒 DTC C0521

Circuit Description

The steering wheel position sensor is a 0-5 volt device used by the Electronic Suspension Control (ESC) module to sense steering wheel position and turning speed. The valid voltage range for the sensor is 0.35-4.75 volts. The output, or signal voltage increases and decreases within the valid voltage range as the steering wheel is turned. The ESC module monitors the two signal voltage values from the steering wheel position sensor, signal 1, and signal 2 circuits. These two signal voltage values should be aligned or synchronized with each other and in the valid voltage range.

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
    • Battery voltage is 11-14 volts.
    • The ignition is ON.

Conditions for Setting the DTC

Signal 1 and signal 2 offset greater than 16 degrees for 2 seconds.

Action Taken When the DTC Sets
    • DTC C0521 is stored in memory.
    • The EVO outputs are disabled.
    • The Electronic Brake Control Module (EBCM) may turn on the SERVICE STABILITY SYSTEM message in the IPC message center.

Conditions for Clearing the DTC
    • A current DTC will clear when the malfunction is no longer present for 10 seconds.
    • 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 if the malfunction exists in the Steering Wheel Position Sensors centered position.

    2.

  2. Tests if the malfunction exist in the Steering Wheel Position Sensors left turn range.

    3.

  3. Tests if the malfunction exist in the Steering Wheel Position Sensors right turn range.

Step

Action

Value(s)

Yes

No

Schematic Reference: Steering Assist Schematics

1

Did you perform the Variable Effort Steering Diagnostic System Check?

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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 on.
  3. Center the steering wheel.
  4. With a scan tool, observe the Steering Wheel Position Sensor signal 1 and Steering Wheel Position Sensor signal 2 data parameters in the RTD/EVO data list.

Does the scan tool display the signal 1 and signal 2 data parameters at the specified value?

signal 1: 4.0 V

signal 2: 2.0 V

Go to Step 3

Go to Step 5

3

Slowly turn the steering wheel to full left lock while observing the signal 1 and signal 2 data parameters.

Do the signal 1 and signal 2 data parameters change state in synchronization with each other and reach the specified value?

signal 1: 2.5 V

signal 2: 4.5 V

Go to Step 4

Go to Step 5

4

Slowly turn the steering wheel to full right lock while observing the signal 1 and signal 2 data parameters.

Do the signal 1 and signal 2 data parameters change state in synchronization with each other and reach the specified value?

signal 1: 1.6 V

signal 2: 1.6 V

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

Go to Step 5

5

Inspect for poor connections at the harness connector of the Steering Wheel Position Sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 6

6

Replace the Steering Wheel Position Sensor. Refer to Steering Wheel Position Sensor or Steering Shaft Lower Bearing Replacement .

Did you complete the replacement?

--

Go to Step 7

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7
  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