Circuit Description
The ESC module uses the Pulse-Width Modulation (PWM) method in order to control each shock absorber solenoid. Switching the voltage ON and OFF at each shock absorber solenoid, or pulse width modulating, limits the amount of current supplied to that particular solenoid. The ESC module periodically commands each shock absorber to an set PWM duty cycle in order to override the normal PWM command. During this set PWM duty cycle, the ESC module is able to perform a diagnostic test on each shock absorber solenoid, and can determine if a malfunction is present. The ESC module is only able to detect certain malfunctions during a given state (ON or OFF). In order to test for the conditions that set a DTC C1727, the ESC module must first command the RR solenoid OFF. The ESC module must be in a command OFF state. If a low voltage level is detected in the RR solenoid drive circuit during the OFF state, the test is again repeated. If the ESC module determines that the voltage levels detected in both tests are lower than expected, a malfunction is present and a DTC will set.
Conditions for Setting the DTC
| • | The ESC module detects a low voltage level (open circuit) on the RR solenoid drive circuit during two diagnostic tests performed. |
| • | Detection for this DTC can only be accomplished when the RR solenoid is in the OFF state (0% duty cycle). |
Action Taken When the DTC Sets
| • | Stores a DTC C1727 in the ESC memory. |
| • | Commands 0% PWM duty cycle in order to disable the RR solenoid. |
| • | Sends a message to the IPC to display the SERVICE RIDE CONTROL message. |
Conditions for Clearing the DTC
| • | The ignition must be cycled before this DTC can change from current to history even if the malfunction is no longer present. |
| • | The ESC module no longer detects a low voltage level (open circuit) on the RR solenoid drive circuit during two diagnostic tests. |
| • | A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present. |
| • | Use the IPC clearing DTC feature. |
| • | Using a scan tool. |
Diagnostic Aids
| • | The following conditions may cause an intermittent malfunction to occur: |
| - | An intermittent open on the solenoid drive or supply lines. |
| - | An internal shock absorber solenoid open or high resistance value. |
| - | An intermittent open in the RTD relay contacts. |
| • | If the conditions for a DTC C1727 are current, the ESC module will disable RR solenoid (commanding 0% duty cycle) and the vehicle will experience a soft ride condition on the RR side of the vehicle. |
| • | If the DTC is a history DTC, the problem may be intermittent. Using a scan tool, cycle the RR shock absorber solenoid while moving the wiring and the connectors. This can often cause the malfunction to appear. |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This step measures the resistance value of the RR shock absorber solenoid.
-
This step checks for an open in the RR shock absorber solenoid circuit.
-
This step checks for an intermittent malfunction and requests a thorough inspection of the related RR shock absorber circuit wiring and connectors.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the RTD Diagnostic System Check performed? | -- | ||
Is the resistance within the specified value? | 9.5-15.5 ohms | |||
Is there continuity? | 9.5-15.5 ohms | |||
Check the RR shock absorber solenoid circuit for an intermittent malfunction. Refer to Diagnostic Aids. Was an intermittent malfunction found and repaired? | -- | |||
5 | Locate and repair the open in CKT 1119 or CKT 1118. Is the circuit repair complete? | -- | -- | |
6 | Replace the RR shock absorber. Refer to Shock Absorber Replacement in Rear Suspension. Is the repair complete? | -- | -- | |
7 |
Is DTC C1727 current? | -- | System OK | |
8 | Replace the ESC module. Refer to Electronic Suspension Control Module Replacement . Is the repair complete? | -- | -- | |
9 |
Is the repair complete? | -- | -- |
