Circuit Description
The strut actuator is controlled by the electronic suspension control (ESC) module with a pulse width modulation (PWM) signal. Switching the voltage ON and OFF at a high frequency (2 kHz), or pulse width modulating, controls the amount of current delivered to the actuator. By controlling the amount of current to the actuator the ESC module controls the damping force in the strut. 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, which is no battery voltage, is one that provides a minimum damping force.
The ESC module periodically commands each strut actuator to a preset PWM duty cycle in order to override the normal PWM command. During this preset PWM duty cycle, the ESC module is able to perform a diagnostic test on each strut actuator to determine if a malfunction is present. The preset PWM command can be either an OFF or ON state duty cycle.
DTC C0577, C0582, C0587, or C0592
In order to test for the conditions that set the DTC C0577, C0582, C0587, or C0592 the following must be present:
The ESC module must first command the strut actuator ON. If the voltage detected in the damper control circuit during the ON state is less than a preset value, the DTC will be set immediately.
DTC C0579, C0584, C0589, or C0594
In order to test for the conditions that set the DTC C0579, C0584, C0589, or C0594 the following must be present:
The ESC module must first command the solenoid ON. If the voltage detected in the damper control circuit during the ON state is between 2 preset values, the test is repeated. If the ESC module again detects voltage between two preset values, a DTC will be set.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C0577 Left Front Solenoid/Motor/Actuator Circuit Low |
| • | DTC C0579 Left Front Solenoid/Motor/Actuator Circuit Open |
| • | DTC C0582 Right Front Solenoid/Motor/Actuator Circuit Low |
| • | DTC C0584 Right Front Solenoid/Motor/Actuator Circuit Open |
| • | DTC C0587 Left Rear Solenoid/Motor/Actuator Circuit Low |
| • | DTC C0589 Left Rear Solenoid/Motor/Actuator Circuit Open |
| • | DTC C0592 Right Rear Solenoid/Motor/Actuator Circuit Low |
| • | DTC C0594 Right Rear Solenoid/Motor/Actuator Circuit Open |
Conditions for Running the DTC
DTC C0577, C0579, C0582, C0584, C0587, C0589, C0592, or C0594
The following conditions must be present to run the DTC:
| • | The ignition is ON. |
| • | The ESC module is in command ON state. |
Conditions for Setting the DTC
DTC C0577, C0582, C0587, or C0592
The following conditions must be present to set the DTC:
| • | The ESC module detects voltage less than a preset value during 2 consecutive ON state tests. |
| • | The fault is detected during 3 consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool. |
DTC C0579, C0584, C0589, or C0594
The following conditions must be present to set the DTC:
| • | The ESC module detects voltage between 2 preset values during 2 consecutive ON state tests. |
| • | The fault is detected during 3 consecutive ignition cycles, or during the same ignition cycle after clearing the DTC with a scan tool. |
Action Taken When the DTC Sets
DTC C0579, C0584, C0589, or C0594
| • | The SERVICE SUSPENSION SYS message will be displayed. |
| • | ALL the strut actuators will be disabled by commanding 0 percent PWM duty cycle. |
| • | The vehicle ride will be soft. |
DTC C0577, C0582, C0587, or C0592
The following conditions must be present to run the DTC:
| • | The SERVICE SUSPENSION SYS and SPEED LIMITED TO XXX messages will be displayed. |
| • | ALL the strut actuators will be disabled by commanding 0 percent PWM duty cycle. |
| • | The damper relay control switch will be opened and the damper relay de-energized. |
| • | The vehicle speed will be limited. |
| • | The vehicle ride will be soft. |
Conditions for Clearing the MIL/DTC
| • | The scan tool can be used to clear the DTC. |
| • | The DTC is saved as history when the ESC module no longer detects the fault during two consecutive diagnostic tests. The DTC will clear if the fault does not return after 50 consecutive ignition cycles. |
Diagnostic Aids
| • | Before proceeding with the diagnostics, ensure the electrical harness connector at the suspect damper is fully engaged by pushing the harness connector toward the damper. If an audible click is heard, or substantial engagement travel is noted, ensure the remaining damper connectors are fully engaged as well. |
| • | When the scan tool is used to clear the DTC, the ESCMs ignition cycle counter is disabled for the remainder of the ignition cycle. This allows the DTC to set upon initial malfunction detection. Once the ignition is cycled the counter resets to 3. |
| • | The scan tool can be used to command the suspect damper On and Off while actuating the suspension and noticing an increase and decrease in damping control. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests for short to ground and short to B+ on the control circuit.
-
Tests for continuity from the ESC module on the control circuit and the low reference circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Suspension Controls Schematics Connector End View Reference: Suspension Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does the resistance measure within the specified range? | 0.5-2 ohms | Go to Step 3 | Go to Step 7 |
Test the damper control circuit of the actuator for a short to ground and short to battery. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 4 | |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 | |
5 | Inspect for poor connections at the actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the ESC module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
7 | Replace the strut/shock absorber. Refer to Shock, Shock Component, and/or Spring Replacement or Shock Absorber Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the ESC module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
