C1720

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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 PWM-ing, 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 C1720, the ESC module must first command the LR solenoid ON. If a high voltage level is detected in the solenoid drive low circuit during the ON state, the test is again repeated. If the ESC module determines that the voltage levels detected in both tests are higher than expected, a malfunction is present and a DTC will set.

Conditions for Setting the DTC
The ESC module detects a high voltage level (short to voltage) on the LR solenoid drive low circuit during two diagnostic tests performed.

Action Taken When the DTC Sets
- Stores a DTC C1720 in the ESC memory.
- Commands 0% PWM duty cycle in order to disable the LR solenoid.
- Sends a message to the IPC to display the SERVICE RIDE CONTROL message.

Conditions for Clearing the DTC
- The ESC module no longer detects a high voltage level (short to voltage) on the LR solenoid drive low circuit during a diagnostic test.
- A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
- The On-Board Diagnostic (clearing DTCs) feature.
- Using a scan tool.

Diagnostic Aids
The following conditions may cause an intermittent malfunction to occur:
- There is an intermittent short to voltage on the LR solenoid drive low circuit.
- The LR solenoid drive (high and low) circuits intermittently shorted together.
- There is a shock absorber solenoid low resistance, internal short, or short to voltage condition.
- If the conditions for a DTC C1720 are current, the ESC module will disable the LR solenoid (commanding 0% duty cycle) and the vehicle will experience a soft ride condition on the LR of the vehicle.
- If the DTC is a history DTC, the problem may be intermittent. Using a scan tool, cycle the LR shock absorber solenoid while moving the wiring and the connectors. This can often cause the malfunction to occur.

Test Description
The numbers below refer to the step numbers on the diagnostic table:
2. This step measures the resistance value of the LR shock absorber solenoid.
3. This step checks for a short to voltage in the LR shock absorber solenoid.
4. This step checks for a short to voltage on CKT 1115.
5. This step checks for a short between CKT 1115 and CKT 1114.
6. This step checks for an intermittent malfunction and requests a thorough inspection of the related LR shock absorber circuit wiring and connectors.