GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Eldorado 🢒 Suspension 🢒 Road Sensing Suspension (RSS) 🢒 DTC C1786 Damper Control Relay Fault

Object Number: 258353 Size: LF

Circuit Description

The high-side (battery) voltage for the CVRSS damper actuators is supplied to the CVRSS control module through the CVRSS Damper Control Relay (RTD Body) circuit. The Damper Control Relay circuit is controlled by the CVRSS module. The CVRSS control module monitors the relay drive circuit and each damper actuator high-side and low-side drive circuits for fault conditions.

DTC C1786 is used to detect a fault condition with the damper control relay contacts and associated wiring.

Conditions for Setting the DTC

The DTC is set when there is a loss of battery voltage on pin D1 of the CVRSS control module.

The DTC turns HISTORY when the CVRSS control module senses a battery voltage at pin D1 after the ignition has been cycled.

Action Taken When the DTC Sets
    • ALL the damper actuators will be disabled by commanding 0 % PWM duty cycle. The vehicle ride will be soft.
    • The vehicle speed will be limited.
    • The SERVICE RIDE CONTROL message will be displayed.

Conditions for Clearing the MIL/DTC
    • Use the scan tool.
    • Use the On-Board diagnostic CLEAR RSS CODES feature.

Test Description

Important: 

   • Do not backprobe the sensors, actuators, or any sealed connectors.
   • When all the diagnostics and repairs are complete, clear the DTCs and verify the operation.

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

  1. This step checks the contacts of the relay for proper operation.

    2.

  2. This step checks CKT 2240 for an open circuit condition.

    3.

  3. This step checks CKT 1333 for an open circuit condition.

Step

Action

Value(s)

Yes

No

1

Was the CVRSS System Check performed?

--

Go to Step 2

Go to Road Sensing Suspension Diagnostic System Check

2

Is DTC C1787 or C1788 set?

--

Go to Diagnostic Trouble Code (DTC) List/Type

Go to Step 3

3

  1. Turn the ignition ON with the engine off.
  2. Measure the voltage at pin D1 of CVRSS control module connector C1 (backprobe).

Is the measurement greater than the specified value?

10 V

Go to Step 6

Go to Step 4

4

  1. Turn the ignition OFF.
  2. Remove the RTD BODY relay.
  3. Measure the voltage at pin B7 of the RTD BODY relay socket.

Is the measurement greater than the specified value?

10 V

Go to Step 5

Go to Step 7

5

  1. Disconnect CVRSS control module connector C1.
  2. Check for continuity between pin C7 of the RTD BODY relay socket and pin D1 of CVRSS control module connector C1 (harness side).

Is there continuity?

--

Go to Step 9

Go to Step 8

6
  1. Turn the ignition OFF.
  2. Remove the RTD BODY relay.
  3. Measure the voltage at pin B7 of the RTD BODY relay socket.

Is the voltage measured more than 0.5 volt higher than the voltage measured in Step 3?

--

Go to Step 9

Go to Step 10

7
  1. Repair the open circuit condition in CKT 2240 or replace the blown fuse.
  2. Install all of the connectors and components that were removed.

Is the repair or replacement complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

8
  1. Repair the open circuit condition in CKT 1333.
  2. Install all of the connectors and components that were removed.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

9
  1. Replace the RTD BODY relay.
  2. Install all of the connectors and components that were removed.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

10
  1. Replace the CVRSS control module. Refer to Electronic Suspension Control Module Replacement .
  2. Install all of the connectors and components that were removed.
  3. Install the scan tool.
  4. Turn the ignition ON with the engine off.

    5. Important: The controller must be calibrated.

  5. Calibrate the CVRSS service controller using the scan tool. Refer to Electronic Suspension Control Module Calibration .

Is the CVRSS control module calibrated?

--

Go to Road Sensing Suspension Diagnostic System Check

--