DTC C1791: Ride Control Switch Contact Fault

The ESC sends a 5-volt reference voltage out to the 3 position ride control switch on ESC connector C1 terminal A7 (Tan/White) wire. This switch allows the driver to select the firmness of his ride (TOUR, SPORT, PERF). The switch grounds the 5-volt reference from terminal A7, through a different resistor in each setting, thereby changing the voltage on terminal A7 according to switch position. In the PERF setting, voltage on terminal A7 should be .5 to 1.5 volts. In the SPORT setting, A7 voltage should be 1.5 to 2.5 volts. In the TOUR setting, the voltage should be 2.5 to 3.5 volts on A7. If the voltage on A7 is between 3.5 and 4.5 volts, for 10 seconds on 4 consecutive ignition cycles, the ESC will set DTC C1791. The ESC will also provide shock absorber control based on the SPORT setting, and send a request to the IPC to display SERVICE RIDE CONTROL message.

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. Turn ignition on, with engine off. Using scan tool, select RIDE CONTROL SWITCH voltage display. Observe voltage with ride control switch in PERF, SPORT and TOUR positions. With the switch in PERF position, voltage should be .5-1.5 volts. In SPORT position, voltage should be 1.5-2.5 volts. In TOUR position, voltage should be 2.5-3.5 volts. If voltages are correct in each position, go to step  6 . If voltage is not within specified range, go to next step.
3. Turn ignition off. Disconnect ride control switch connector. Ensure ride control switch is not in-between switch positions. Measure resistance between terminals of ride control switch (component side) with switch in PERF, SPORT and TOUR positions. With switch in PERF position, resistance should be 250-350 ohms. With switch in SPORT position, resistance should be 80-180 ohms. With switch in TOUR position, resistance should be 25-75 ohms. If resistance is as specified, go to next step. If resistance is not as specified, go to step  10 .
4. Turn ignition on, with engine off. Measure voltage between ground and 5-volt reference circuit (Tan/White wire) of ride control switch harness connector. See WIRING DIAGRAMS  . If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step  8 .
5. Using scan tool, monitor ride control switch voltage. Connect fused jumper wire between ride control switch harness connector Tan/White and Pink/White wires. If voltage is 0-0.5 volt, go to next step. If voltage is not 0-0.5 volt, go to step  9 .
6. Check ride control switch and circuits for intermittent operation. See NOTES ON INTERMITTENTS  under DIAGNOSIS & TESTING. See WIRING DIAGRAMS  . After repairs, go to step  12 . If switch and circuits are okay, go to next step.
7. Turn ignition off. Reinstall/reconnect all components/connectors that were removed or disconnected. Turn ignition on. Using scan tool, select clear all DTCs. If DTC C1791 is current, go to step  11 . If DTC C1791 is not current, system is functioning properly.
8. Check circuit No. 1384 (Tan/White wire) for short to ground, short to voltage or an open between ride control switch and RTD control module connector C1, terminal A7. See WIRING DIAGRAMS  . After repairs, go to step  12 . If circuit No. 1384 is okay, go to step  11 .
9. Check circuit No. 1385 (Pink/Black wire) for short to voltage or an open between ride control switch and RTD control module connector C2, terminal D7. See WIRING DIAGRAMS  . After repairs, go to step  12 . If circuit No. 1385 is okay, go to step  11 .
10. Replace ride control switch. See RTD CONTROL SWITCH  under REMOVAL & INSTALLATION. After repairs, go to step  12 .
11. Replace RTD control module. See RTD CONTROL MODULE  under REMOVAL & INSTALLATION. After repairs, go to next step.
12. Turn ignition off. Reinstall/reconnect all components/connectors. Using scan tool, clear all DTCs.