GM Service Manual Online
For 1990-2009 cars only

Object Number: 603744  Size: LF
Suspension Controls Components
Suspension Control Module, Shock Solenoid Valves

Circuit Description

The suspension control module provides a common regulated voltage of approximately 5 volts to all four of the (body-to-wheel) position sensors, RTD air pressure sensor and the steering handwheel position/speed sensor. The suspension control module monitors this reference voltage for any malfunctions that could prevent it from outputting a regulated 5 volts.

For a full system schematic refer to: Suspension Controls Schematics .

Conditions for Running the DTC

Continuously with the ignition on.

Conditions for Setting the DTC

The suspension control module senses a sensor reference voltage of less than 4.0 volts or greater than 6.0 volts.

Action Taken When the DTC Sets

    • DTC C0870 will be stored in memory.
    • Disable all EVO outputs.
    • Disable all compressor leveling functions, and assume default pressure.
    • Disable all shock solenoid valve outputs.
    • The SERVICE RIDE CONTROL message will be displayed.

Conditions for Clearing the MIL/DTC

    • The suspension control module senses the correct voltage output to the position sensors upon the next ignition cycle.
    • A history DTC will clear after not seeing the malfunction for 100 consecutive ignition cycles.
    • Using a scan tool.

Diagnostic Aids

    • The following conditions may cause a malfunction to occur:
       - A short to voltage in any one of the (body-to-wheel) position sensor reference voltage circuit.
       - A short to ground in any one of the (body-to-wheel) position sensor reference voltage circuit.
    • If the circuit is shorted to ground the scan tool will display all position sensor voltage as zero.
    • If the circuit is shorted to a unwanted voltage source, the scan tool may display all position sensor voltage as that voltage.
    • A short to voltage in the 5 volt reference of the RTD air pressure sensor.
    • A short to ground in the 5 volt reference of the RTD air pressure sensor.
    • A short to voltage in the 5 volt reference of the steering handwheel position/speed sensor.
    • A short to ground in the 5 volt reference of the steering handwheel position/speed sensor.
    • A intermittent malfunction or DTC may cause a random firm/soft ride condition.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Tests whether the condition is module, system, or condition related.

  2. Tests whether the condition has been corrected or identified as specified in the supporting text.

  3. Tests all position sensors reference voltage circuits.

  4. Tests the 5 volt reference circuit of the steering handwheel position/speed sensor for a short to ground and a short to voltage.

  5. Tests the 5 volt reference circuit of the RTD air pressure sensor for a short to ground and a short to voltage.

  6. Clear DTCs and checks to see if DTC will reset.

Step

Action

Value(s)

Yes

No

1

Did you perform the RTD Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, monitor the DTC Information for DTC C0870 in the Suspension Control Module.

Does the scan tool indicate that DTC C0870 is current?

--

Go to Step 4

Go to Step 3

3

Since most occurrences of this DTC are caused by a short to ground or short to voltage in a sensor reference voltage circuit, review the RTD System or, with the customer to verify the conditions under which the DTC set.

Did vehicle operation cause this DTC to set?

--

Go to Diagnostic Aids

Go to Step 4

4

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within normal operating conditions.

Does the DTC reset?

--

Go to Step 5

System OK

5

Test all 4 (body-to-wheel) position sensor 5 volt reference circuits for a short to ground and a short to voltage.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 6

6

Test the steering handwheel position/speed sensor 5 volt reference circuit for a short to ground and a short to voltage.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

7

Test the RTD air pressure sensor 5 volt reference circuit for a short to ground and a short to voltage.

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 9

8

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within normal operating conditions.

Does the DTC reset?

--

Go to Step 9

System OK

9

Replace the suspension control module. Refer to Electronic Suspension Control Module Replacement .

Did you complete the replacement?

--

System OK

--