GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Yukon XL - 2WD 🢒 Suspension 🢒 Real Time Damping (RTD) 🢒 DTC C0870

Circuit Description

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

Conditions for Running the DTC

Continuously with the ignition on.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets
    • Disable all EVO outputs.
    • Disable all compressor leveling functions, and assume default pressure.
    • Disable all suspension damper solenoid outputs.
    • The SERVICE RIDE CONTROL message will be displayed.
    • Stores a DTC C0870 in the ESC module memory.

Conditions for Clearing the DTC
    • The ESC module senses the correct voltage output to the suspension position sensors upon the next ignition cycle.
    • Using a scan tool.
    • A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

Important: Ignition cycle counting is used by the ESC module to detect faults in the system. The objective is to eliminate false/intermittent codes while maintaining an acceptable level of system performance. The operation of the ignition cycle counting requires that a fault condition be present for four consecutive ignition cycles before it will set the fault code and display the "SERVICE RIDE CONTROL" message. If a fault code is present (without a fault being current), the system will go into one or more degraded modes without displaying a message. Resetting the ignition cycle counter is done by clearing codes with a scan tool. Clearing codes will override ignition cycle counting for one ignition cycle. Therefore, a fault condition will set the fault code immediately if it occurs on the first ignition cycle after the codes are cleared.

    • The following conditions may cause a malfunction to occur:
       - A short to voltage in any one of the body-to-wheel suspension position sensor reference voltage circuit.
       - A short to ground in any one of the body-to-wheel suspension position sensor reference voltage circuit.
    • If the circuit is shorted to ground, the scan tool will display all suspension position sensor voltage as zero.
    • If the circuit is shorted to an unwanted voltage source, the scan tool may display all suspension position sensor voltage as that voltage.
    • A short to voltage in the 5 volt reference of the air pressure sensor.
    • A short to ground in the 5 volt reference of the 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 numbers below refer to the step numbers on the diagnostic table.

  1. Tests all suspension position sensors reference voltage circuits.

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

    3.

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

    4.

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

Step

Action

Yes

No

Schematic Reference: Suspension Controls Schematics Automatic Level Control Schematics Steering Assist Schematics

1

Did you perform the RTD Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Real Time Damping

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the suspension position sensors, air pressure sensor, and steering wheel position sensor 5 volt reference data parameters in the ESC module data list.

Does the scan tool indicate that all the above mentioned data parameters are less than 4 volts or greater than 6 volts?

Go to Step 3

Go to Diagnostic Aids

3

Test all 4 body-to-wheel suspension 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 7

Go to Step 4

4

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 7

Go to Step 5

5

Test the 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 7

Go to Step 6

6

Replace the ESC module. Refer to Electronic Suspension Control Module Replacement .

Did you complete the replacement?

Go to Step 7

--

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