Code
C1780
HUMMER
C — Chassis
Loss of Steering Position Signal
AI status
Completed
Completed
100%
Causes
- Steering angle/position sensor electrical failure
- Open, shorted, or intermittent wiring between the sensor and control module
- Poor or corroded connector/terminal at the sensor or control module
- Faulty steering column sensor (potentiometer/hall-effect/encoder)
- Failed steering control module or related ECU
- Loss of CAN/communication bus carrying steering position data
Symptoms
- Steering/ESP/ABS or EPS warning lamp illuminated
- Loss or reduction of electric power steering assist or erratic assist
- Vehicle stability/traction control disabled or functions limited
- Steering angle/position reading missing or incorrect in scan tool live data
- Steering feel changes or unexpected behavior during turns
- Diagnostic trouble codes related to steering angle, ABS, or network communication present
What to check
- Read and record all related trouble codes and freeze-frame data using a capable scan tool
- Check battery voltage and charge state; low system voltage can cause communication errors
- Inspect steering column and sensor connector for corrosion, bent pins, or poor mating
- Visually inspect wiring harness along steering column for chafing, breaks, or rubbed-through insulation
- Verify power and ground to the steering position sensor (check fuses and grounds)
- Scan tool: view live steering angle/position data while rotating steering wheel and compare to expected movement
Signal parameters
- Steering angle/position sensor supply: typically battery/ignition 5 V or regulated reference — verify exact value in service manual
- Sensor ground: near 0 V (low-resistance chassis ground)
- Analog position signal (if used): typical range ~0.5–4.5 V across full travel — exact range depends on sensor type
- Digital sensors: CAN or LIN message carrying steering angle — expect regular messages (e.g., 10–100 Hz) when key ON and steering being moved
- Resistance/continuity (for potentiometer-type): manufacturer-specific; check service manual for expected ohms and ramp measurements while rotating column
Diagnostic algorithm
- Connect a full-function scan tool and record C1780 and any related codes; note freeze frame and live data
- Verify battery voltage is within specification (12.4–14.5 V) and that charging system is healthy
- Inspect and secure connectors at the steering angle/position sensor and steering control module; disconnect, inspect pins, clean and reconnect
- Visually inspect the wiring harness from sensor to module for damage, flex points, or pinched sections; repair any damaged wiring
- With key ON, backprobe sensor power, ground and signal lines. Confirm reference voltage present and stable, ground continuity, and expected signal waveform or voltage while rotating the steering wheel
- If sensor signal is missing or out of range, wiggle the harness and column to reproduce the fault; if intermittent, repair the harness or connector
- If analog signal cannot be verified and wiring checks good, remove and bench-test or replace the steering angle sensor per OEM instructions
- If sensor tests ok, verify steering control module receives the signal (monitor live data for the module). If module shows no input while sensor is good, suspect module fault or bus communication issue
- Check CAN/LIN communication: verify bus voltage levels and that other modules (ABS, BCM, ECM) communicate normally. Repair bus faults (shorts/opens/termination) as needed
- After repair or sensor/module replacement, perform required steering angle sensor calibration/relearn with scan tool (zeroization) and follow OEM procedures
- Clear codes and test drive to verify fault does not return and vehicle stability/steering systems operate normally
- If code persists after wiring/sensor/service, consider replacing steering control module and program/configure as required by manufacturer
Likely causes
- Damaged steering angle sensor on the steering column or rack (physical damage or internal failure)
- Broken/abraded wiring harness in steering column (common at flex points)
- Corroded pins in sensor or module connectors causing intermittent contact
- Blown fuse, poor ground, or loss of sensor supply voltage
- Control module fault or firmware/communication errors on CAN bus
- Recent steering/airbag/column service done without performing sensor relearn/calibration
Fault status
Status
Stored when the steering position/angle signal is missing, out of expected range, or not received by the steering control module/vehicle network.
Repair difficulty: Medium
Diagnostic time: 1–3 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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Code
C1780
Other
C — Chassis
Temperature Select Failure
AI status
Completed
Completed
100%
Causes
- Steering angle/position sensor electrical failure
- Open, shorted, or intermittent wiring between the sensor and control module
- Poor or corroded connector/terminal at the sensor or control module
- Faulty steering column sensor (potentiometer/hall-effect/encoder)
- Failed steering control module or related ECU
- Loss of CAN/communication bus carrying steering position data
Symptoms
- Steering/ESP/ABS or EPS warning lamp illuminated
- Loss or reduction of electric power steering assist or erratic assist
- Vehicle stability/traction control disabled or functions limited
- Steering angle/position reading missing or incorrect in scan tool live data
- Steering feel changes or unexpected behavior during turns
- Diagnostic trouble codes related to steering angle, ABS, or network communication present
What to check
- Read and record all related trouble codes and freeze-frame data using a capable scan tool
- Check battery voltage and charge state; low system voltage can cause communication errors
- Inspect steering column and sensor connector for corrosion, bent pins, or poor mating
- Visually inspect wiring harness along steering column for chafing, breaks, or rubbed-through insulation
- Verify power and ground to the steering position sensor (check fuses and grounds)
- Scan tool: view live steering angle/position data while rotating steering wheel and compare to expected movement
Signal parameters
- Steering angle/position sensor supply: typically battery/ignition 5 V or regulated reference — verify exact value in service manual
- Sensor ground: near 0 V (low-resistance chassis ground)
- Analog position signal (if used): typical range ~0.5–4.5 V across full travel — exact range depends on sensor type
- Digital sensors: CAN or LIN message carrying steering angle — expect regular messages (e.g., 10–100 Hz) when key ON and steering being moved
- Resistance/continuity (for potentiometer-type): manufacturer-specific; check service manual for expected ohms and ramp measurements while rotating column
Diagnostic algorithm
- Connect a full-function scan tool and record C1780 and any related codes; note freeze frame and live data
- Verify battery voltage is within specification (12.4–14.5 V) and that charging system is healthy
- Inspect and secure connectors at the steering angle/position sensor and steering control module; disconnect, inspect pins, clean and reconnect
- Visually inspect the wiring harness from sensor to module for damage, flex points, or pinched sections; repair any damaged wiring
- With key ON, backprobe sensor power, ground and signal lines. Confirm reference voltage present and stable, ground continuity, and expected signal waveform or voltage while rotating the steering wheel
- If sensor signal is missing or out of range, wiggle the harness and column to reproduce the fault; if intermittent, repair the harness or connector
- If analog signal cannot be verified and wiring checks good, remove and bench-test or replace the steering angle sensor per OEM instructions
- If sensor tests ok, verify steering control module receives the signal (monitor live data for the module). If module shows no input while sensor is good, suspect module fault or bus communication issue
- Check CAN/LIN communication: verify bus voltage levels and that other modules (ABS, BCM, ECM) communicate normally. Repair bus faults (shorts/opens/termination) as needed
- After repair or sensor/module replacement, perform required steering angle sensor calibration/relearn with scan tool (zeroization) and follow OEM procedures
- Clear codes and test drive to verify fault does not return and vehicle stability/steering systems operate normally
- If code persists after wiring/sensor/service, consider replacing steering control module and program/configure as required by manufacturer
Likely causes
- Damaged steering angle sensor on the steering column or rack (physical damage or internal failure)
- Broken/abraded wiring harness in steering column (common at flex points)
- Corroded pins in sensor or module connectors causing intermittent contact
- Blown fuse, poor ground, or loss of sensor supply voltage
- Control module fault or firmware/communication errors on CAN bus
- Recent steering/airbag/column service done without performing sensor relearn/calibration
Fault status
Status
Stored when the steering position/angle signal is missing, out of expected range, or not received by the steering control module/vehicle network.
Repair difficulty: Medium
Diagnostic time: 1–3 hours
Similar codes
Repair manuals
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