DTC C1721: Left Rear Damper Solenoid (Short To Ground)

The ESC module sends a Pulse Width Modulated (PWM) signal to shock absorbers to control damping. Occasionally, to test integrity of system, ESC module commands each shock to a predetermined PWM duty cycle. It then looks at voltage on the solenoid trigger wire to see if it is lower than expected. If it is lower on 2 separate tests, ESC module assumes trigger wire is shorted to ground, and sets a code for the corresponding shock absorber. If failed shock is the drivers rear, a DTC C1721 will be set. The ESC will then command PWM duty cycle for all shock absorbers to 0, causing a soft ride. It will also send a message to IPC to display SERVICE RIDE CONTROL and SHOCKS INOPERATIVE messages, as well as limit vehicle speed to 80 MPH.

1. Perform RTD diagnostic system check. See RTD DIAGNOSTIC SYSTEM CHECK  under DIAGNOSIS & TESTING. After performing RTD diagnostic system check, go to next step.
2. Using scan tool, retrieve DTCs. If DTC C1786, C1787 or C1788 is set, go to appropriate DTC for diagnosis. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION  table under DIAGNOSIS & TESTING. If DTC C1786, C1787 or C1788 is not set, go to next step.
3. Turn ignition off. Disconnect left rear damper solenoid connector. Measure resistance between solenoid connector terminals (solenoid side). If resistance is 9.5-15.5 ohms, go to next step. If resistance is not 9.5-15.5 ohms, replace damper (shock absorber). See SHOCK ABSORBER  under REMOVAL & INSTALLATION. After repairs, go to step  8 .
4. Check for continuity between ground and left rear damper solenoid connector Dark Blue/White wire (solenoid side). If continuity exists, replace damper (shock absorber). See SHOCK ABSORBER  under REMOVAL & INSTALLATION. After repairs, go to step  8 . If continuity does not exist, go to next step.
5. Reconnect left rear damper solenoid connector. Disconnect RTD module connector C2. Check for continuity between ground and harness side of RTD module connector C2, terminal C3 (Dark Green wire) and also C4 (Dark Blue/White wire). If continuity exists, locate and repair short to ground in Dark Green or Dark Blue/White wire between RTD module and damper solenoid and go to step  8 . If continuity does not exist, go to next step.
6. Check left rear damper circuit for intermittent malfunction. Using scan tool, cycle left rear damper solenoid while moving wiring and connectors. If intermittent malfunction is found and repaired, go to step  8 . If intermittent malfunction is not found and repaired, go to next step.
7. Turn ignition off. Connect or install any connector or components that were disconnected or removed. Turn ignition on. Using scan tool, clear all DTCs. Cycle left rear damper solenoid for 60 seconds. If DTC C1721 is set, replace RTD control module. See RTD CONTROL MODULE  under REMOVAL & INSTALLATION. After repairs, go to next step. If DTC C1721 is not set, system is functioning properly.
8. Turn ignition off. Connect or install any connector or components that were disconnected or removed. Turn ignition on. Using scan tool, clear all DTCs.