GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The Speed dependent Steering System (MAGNASTEER®) incorporates its controller into the EBCM. The EBCM controls the amount of current supplied to the MAGNASTEER® actuator based on input from the wheel speed sensors.

MAGNASTEER® 2 also uses inputs from the wheel speed sensors along with added input from the Steering Wheel Position Sensor.

Conditions for Setting the DTC

One or both of the MAGNASTEER® actuator circuit wires become open or shorted.

Action Taken When the DTC Sets

A malfunction DTC is stored. No ABS or Car Icon (TCS indicator) indicators are turned on but MAGNASTEER® is disabled. ABS/TCS remains functional.

Conditions for Clearing the DTC

    • Condition for DTC is no longer present and scan tool clear DTC function is used.
    • Fifty ignition cycles have passed with no DTC(s) detected.

Diagnostic Aids

    • It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
    • An intermittent malfunction can be caused by poor connections, broken insulation, or a wire that is broken inside the insulation.
    • If an intermittent malfunction exists refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. This step uses the scan tool to check the Magna Steer Feedback Current parameter.

  2. This step checks for an open in the variable effort steering actuator and circuit.

Step

Action

Value(s)

Yes

No

Schematic Referance: Steering Assist Schematics

1

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. Start the engine.
  3. With a scan tool, observe the MAGNASTEER® Commanded Current and MAGNASTEER® Feedback Current parameters in the MAGNASTEER® data list.
  4. Carefully test drive the vehicle so that the MAGNASTEER® Commanded Current is greater than 826 mA.

Does the scan tool indicate that the MAGNASTEER® Feedback Current is greater than the specified value?

155 mA

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 variable effort steering actuator connector.
  3. Measure the resistance across the variable effort steering actuator.

Does the resistance measure within the specified range?

1.6-3.1 ohms

Go to Step 4

Go to Step 5

4

Test both variable effort steering actuator control circuits for a short to ground, short to voltage, an or open between the EBCM and the variable effort steering actuator pigtail connector. Refer to Circuit Testing and Wiring Repairs in Wiring System.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 6

5

Inspect for poor connections at the harness connector of the variable effort steering actuator. 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 9

Go to Step 7

6

Inspect for poor connections at the harness connector of the EBCM. 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 9

Go to Step 8

7

Replace the variable effort steering actuator. Refer to Steering Gear Replacement in Power Steering System.

Did you complete the repair?

--

Go to Step 9

--

8

Important: Perform the setup procedure for the EBCM. An unprogrammed EBCM will result in the following conditions:

   • Inoperative or poorly functioning DRP/ABS/TCS/VSES/VES (if equipped)
   • Set DTC C1248 EBCM Turned the Red Brake Warning Indicator On
   • Set DTC C1255 EBCM Internal Malfunction

Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brake System.

Did you complete the repair?

--

Go to Step 9

--

9

  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