What Does C1124 Mean?
This code indicates the ABS or transfer case control module has detected a missing or faulted input shaft speed signal. The input shaft speed sensor monitors transmission input shaft RPM, which is critical for traction control calculations and transfer case engagement timing. A loss of this signal prevents the module from accurately determining wheel slip and drivetrain speed ratios.
Common Causes
35%
Failed input shaft speed sensor due to internal coil failure or magnetic element degradation
25%
Damaged or corroded wiring harness between the speed sensor and control module, often from transmission fluid leaks or heat exposure
20%
Damaged or contaminated reluctor ring on the input shaft causing erratic or missing signal
15%
Corroded or backed-out connector at the sensor or control module end
5%
Control module internal circuit failure on the speed sensor input channel
Diagnostic Steps
1
Step 1: Visually inspect the input shaft speed sensor and its connector at the transmission housing for signs of fluid contamination, corrosion, or physical damage. Check that the sensor is fully seated in its bore.
2
Step 2: Using a multimeter, measure the resistance across the input shaft speed sensor terminals (typical range 800-1600 ohms depending on manufacturer). An open or shorted reading indicates sensor failure.
3
Step 3: With the sensor connected, backprobe the signal wire at the control module connector and use an oscilloscope to verify an AC sine wave signal while rotating the input shaft. Expected amplitude is 0.2-1.5V AC.
4
Step 4: Check wiring continuity from sensor connector to control module connector. Test for shorts to ground and shorts to battery voltage on both signal and ground wires.
5
Step 5: Clear codes, test drive the vehicle, and monitor live data for input shaft speed signal presence and stability.
Estimated Repair Cost
$120 - $400
Parts + labor, varies by vehicle and location
This code indicates the ABS or transfer case control module has detected a missing or faulted input shaft speed signal. The input shaft speed sensor monitors transmission input shaft RPM, which is critical for traction control calculations and transfer case engagement timing. A loss of this signal p...
The most common cause of C1124 (Input shaft speed signal missing/faulted) is: Failed input shaft speed sensor due to internal coil failure or magnetic element degradation
Typical repair costs for C1124 range from $120 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Traction control and possibly transfer case operation may be disabled. Vehicle is drivable but may exhibit reduced stability on slippery surfaces. Repair within one week.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1124 to identify the root cause.
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Quick Info
Category
Chassis
System
Traction Control / Transfer Case System
Difficulty
Type
Manufacturer
Recommended Tools
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