Code C1780: Steering Sensor Input Fault

Perform CVRSS system check. See CVRSS SYSTEM CHECK . After performing CVRSS system check, go to next step.
If Code C1781 is set, go to applicable code for diagnosis. See CODE DESCRIPTION table under SELF-DIAGNOSTICS. If Code C1781 is not set, go to next step.
Turn ignition on, with engine. Center steering wheel and verify front wheels are straight. Using scan tool, monitor RSS DATA RS D15. If voltage is 2-3 volts, go to step 14). If voltage is less than 2 volts or more than 3 volts, go to next step.
Turn ignition off. Center steering wheel and verify front wheels are straight. Disconnect steering sensor connector. Using DVOM, measure resistance between 5-volt reference circuit (Gray wire) and ground circuit (Orange/Black wire) of steering sensor connector (component side). See WIRING DIAGRAMS . If resistance is 8000-12,000 ohms, go to next step. If resistance is less than 8000 or more than 12,000 ohms, go to step 17).
Using DVOM, measure resistance between steering signal circuit (Light Blue wire) and ground circuit (Orange/Black wire) of steering sensor connector (component side). See WIRING DIAGRAMS . If resistance is 4000-6000 ohms, go to next step. If resistance is less than 4000 or more than 6000 ohms, go to step 17).
Check for steering sensor misalignment. If steering sensor is misaligned, go to step 15). If steering sensor is not misaligned, go to next step.
Disconnect 24-pin CVRSS control module connector C2. Check continuity between the following circuits of CVRSS control module harness connector C2 and ground. See WIRING DIAGRAMS .
- 5-volt reference circuit (Gray wire)
- Steering signal circuit (Light Blue wire)
- Ground circuit (Orange/Black wire)
If continuity does not exist on all circuits, go to next step. If continuity exists on any circuit, go to step 11).
Check for opens in 5-volt reference circuit (Gray wire), steering signal circuit (Light Blue wire), and ground circuit (Orange/Black wire). If open is present on any circuit, go to step 10). If all circuits are okay, go to next step.
Turn ignition on, with engine off. Check for short to voltage in 5-volt reference circuit (Gray wire), steering signal circuit (Light Blue wire), and ground circuit (Orange/Black wire). If voltage is present on any circuit, go to step 12). If voltage is not present on any circuit, go to step 13).
Repair open in affected circuit. After repairs, perform CVRSS SYSTEM CHECK .
Repair short to ground in affected circuit. After repairs, perform CVRSS SYSTEM CHECK .
Repair short to voltage in affected circuit. After repairs, perform CVRSS SYSTEM CHECK .
Turn ignition off. Reinstall/reconnect all components/connectors. Clear codes. Drive vehicle faster than 50 MPH for more than 15 seconds. Display CVRSS codes. If Code C1780 is set, go to step 18). If Code C1780 is not set, perform CVRSS SYSTEM CHECK .
Using scan tool, monitor RSS DATA RS D15 while rotating steering wheel. See Fig 1 . If steering sensor output voltage is as specified, go to step 16). If steering sensor output voltage is not as specified, go to step 20).

Fig 1: Steering Sensor Output Voltage
Courtesy of GENERAL MOTORS CORP.
Realign steering sensor. See STEERING AUTOCENTER under ADJUSTMENTS. After repairs, perform CVRSS SYSTEM CHECK .
Check for intermittent short to ground, short to voltage or open in 5-volt reference circuit (Gray wire), steering signal circuit (Light Blue wire), and ground circuit (Orange/Black wire). Repair as necessary. After repairs, perform CVRSS SYSTEM CHECK .
Turn ignition off. Replace steering sensor. Perform steering autocenter adjustment. See STEERING AUTOCENTER under ADJUSTMENTS. After repairs, perform CVRSS SYSTEM CHECK .
Turn ignition off. Replace CVRSS control module. Reinstall/reconnect all components/connectors. Install scan tool. Turn ignition on, with engine off. Calibrate NEW CVRSS control module. See CALIBRATING CVRSS CONTROL MODULE under ADJUSTMENTS. Perform CVRSS SYSTEM CHECK .