1999 STS Suspension Problem

[laurieandphil]

Hi, I'm new to the group and have a question. My '99 STS has 140K miles on it and the ride comfort has deteriorated dramatically. I've gotten the "Service Suspension" display on the cluster, and have pulled the codes for the RSS. They are as follows:

C1711 - Left Front Damper Actuator Short Circuit to Ground
C1782 - ICCS2 DL Left Output Short Circuit to Bat

The rear shocks were leaking air (load leveling) and the front struts were allowing quite a bounce, so I replaced all 4 corners...yeah $2k spent on parts. Anyway, I can reset the RSS codes, but C1782 never goes away. C1711 will clear, but will reappear pretty quickly. Any ideas on where to start with diagnosis? Is one error causing the other?

Thanks!

[Ian-STS99]

Check the connectors for the shocks, and look for any broken wires.

Other than that, you might have a defective shock, if so you need to get it changed out. If you had a dealer install them, get them to check it all out.

[laurieandphil]

I had the same codes before I replaced the struts/shocks. The connectors were clean and in good shape, at all 4 corners of the car. Any ideas on why he codes still appear?

[ben.gators]

Originally Posted by laurieandphil

I had the same codes before I replaced the struts/shocks. The connectors were clean and in good shape, at all 4 corners of the car. Any ideas on why he codes still appear?

Dealer or mechanic shop that has installed new shocks and struts is in charge, if I were in you shoes I will immediately drive there and ask them what are these codes in my car?! You have spend a lot of money and they need to take care of it any way!

[Ranger]

Have then check the wiring. Especially on the LF. There is a short circuit there.

[laurieandphil]

I installed the shocks and struts myself. The connectors were clean and in good shape. I will trace the wires from the LF strut connector to the Braking module. Do you think a C1711 code could force a C1782 code? My big fear is that the control module is on it's way out (or already gone).

I'll check for damaged wires. Any other advice for troubleshooting these 2 codes?

Thanks!

[Ian-STS99]

Also check out your load level unit that has a small rod that connects to the lower arm on the left side, make sure there are no broken wires there etc.

[Ranger]

Do you think a C1711 code could force a C1782 code?

BTSOM! I don't know the system that well. A FSM is by far the best way to troubleshoot any DTC. It has a step by step procedure.

BTW, a little more descriptive title would be helpful and might get more responses.. I'll edit it for you.

[wabbas]

Document ID # 295559

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DTC C1711 LF Damper Actuator Short CKT to Ground
Circuit Description




The LF damper actuator is driven by the CVRSS module via a method known as Pulse-Width Modulation (PWM). Battery voltage is modulated (switched on and off) at a high frequency (2.0 kHz), thus controlling the amount of current delivered to the actuator. By controlling the amount of current to the actuator the CVRSS module can then control the damping force in the damper. A higher level of damping force is achieved by providing correspondingly higher current levels, relating to higher percentages of PWM duty cycle.

The default damper state (with no battery voltage, and thus no current, provided to the attached actuator) is one that provides a minimum damping force.

Conditions for Setting the DTC
The DTC is set when the CVRSS module measures a feedback voltage lower than a preset value during two consecutive OFF-state damper diagnostic test procedures.

The DTC is set when the CVRSS module performs a test procedure on each damper actuator approximately every 16 seconds. During this test procedure the damper actuator is briefly energized (ON-state test) and de-energized (OFF-state test). If, twice consecutively, the feedback voltage during the OFF-state test is below the fault threshold, the corresponding DTC is set.

The DTC turns HISTORY when the CVRSS module no longer senses a short circuit condition to ground on the damper low-side drive.

Action Taken When the DTC Sets
The SERVICE RIDE CONTROL message will be displayed.
ALL the damper actuators will be disabled by commanding 0 percent PWM duty cycle.
The damper high-side will be opened.
The vehicle speed will be limited.
The vehicle ride will be soft.
Conditions for Clearing the MIL/DTC
Use the scan tool.
Use the On-Board diagnostic CLEAR RSS CODES feature.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.


Important
Intermittent connections in CKTs 1112 or 1333, or with the RTD Body Relay may cause this DTC to set. If this DTC is displayed as HISTORY, look for intermittents in CKTs 1112 or 1333, or the RTD Body Relay.


This step checks for a fault in the damper relay (RTD Body Relay) circuit.

This step checks for an internal open circuit condition in the actuator.

This step checks for short circuit to ground circuit condition in the actuator pigtail harness.

This step checks the CVRSS actuator harness (CKT 1005) for a short to ground condition with the actuator disconnected.


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

Step Action Value(s) Yes No
1 Was the Road Sensing Suspension Diagnostic System Check performed? -- Go to Step 2 Go to Road Sensing Suspension Diagnostic System Check
2 Is DTC C1786, C1787, or C1788 set (CURRENT or HISTORY)? -- Go to Diagnostic Trouble Code (DTC) List/Type Go to Step 3
3 Turn the ignition OFF.
Disconnect the connector from the LF damper actuator.
Measure the resistance between pin A and pin B of the LF damper actuator (actuator side) with a J 39200 DMM.
Is the resistance value displayed within the specified range? 9.5-15.5 ohms Go to Step 4 Go to Step 8
4 Measure the resistance from the damper actuator connector B (actuator side) to ground with a DMM. Is the resistance the value specified? OL Go to Step 5 Go to Step 8
5 Disconnect CVRSS control module connector C1.
Measure the resistance from the CVRSS module connector C1, terminal D12 (harness side), to ground with a DMM.
Is the resistance the value specified? OL Go to Step 7 Go to Step 6
6 Repair the short circuit to ground in CKT 1005, between CVRSS connector C1, terminal D12 and the actuator connector B. Is the repair complete? -- Go to Road Sensing Suspension Diagnostic System Check --
7 Check CVRSS control module connector C1 and the LF Damper actuator connector for debris and corrosion.
Check for intermittent poor electrical connections.
Check for intermittent short circuit conditions or chafed wires.
Turn the ignition ON with the engine off.
Clear DTCs and then wait 90 seconds. Refer to Clearing DTCs .
Check the DTCs. Refer to Displaying Diagnostic Trouble Codes (DTC) .
Is DTC C1711 or C1712 set? -- Go to Step 9 Go to Road Sensing Suspension Diagnostic System Check
8 Replace the LF damper. Refer to Strut Assembly Replacement . Is the replacement complete? -- Go to Road Sensing Suspension Diagnostic System Check --
9 Turn the ignition OFF.
Replace the CVRSS control module. Refer to Electronic Suspension Control Module Replacement .
Install all of the connectors and components that were removed.
Install the scan tool.
Turn the ignition ON with the engine off.

Important
The controller must be calibrated.


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 --

© Copyright General Motors Corporation. All Rights Reserved.


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Document ID # 295559