What Does C1429 Mean?
The input shaft speed sensor circuit within the transfer case or transmission has failed. The control module is not receiving a valid speed signal from the input shaft, which is essential for calculating gear ratios, controlling shift timing, and managing torque distribution. The driver may experience harsh or erratic shifting, loss of all-wheel-drive or four-wheel-drive functionality, and illumination of drivetrain warning indicators.
Common Causes
35%
Failed input shaft speed sensor with internal open or short circuit
25%
Damaged or corroded wiring between the sensor and control module
20%
Contaminated or debris-covered sensor tip preventing signal generation
15%
Damaged reluctor ring (tone wheel) on the input shaft
5%
Control module input driver failure
Diagnostic Steps
1
With the sensor connector disconnected, measure the input shaft speed sensor resistance — typical values range from 800–1400 ohms for a magnetic pickup type. Out-of-range readings indicate sensor failure.
2
Check for an AC voltage signal at the sensor connector while spinning the input shaft (vehicle raised, transmission in neutral) — you should see a pulsing AC signal that increases with speed.
3
Inspect the sensor connector and wiring for corrosion, oil contamination, damaged pins, or broken wires. Transmission fluid leaking past the sensor seal can damage the connector.
4
Remove the sensor and inspect the tip for metallic debris accumulation and check the reluctor ring through the sensor bore for missing or damaged teeth.
5
Verify proper sensor air gap if adjustable — typical specification is 0.020–0.050 inches between the sensor tip and reluctor ring teeth.
Estimated Repair Cost
$100 - $500
Parts + labor, varies by vehicle and location
The input shaft speed sensor circuit within the transfer case or transmission has failed. The control module is not receiving a valid speed signal from the input shaft, which is essential for calculating gear ratios, controlling shift timing, and managing torque distribution. The driver may experien...
The most common cause of C1429 (Input-shaft-speed input circuit failure) is: Failed input shaft speed sensor with internal open or short circuit
Typical repair costs for C1429 range from $100 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle can be driven but may have degraded drivetrain performance. Four-wheel-drive or all-wheel-drive functionality may be lost, reducing traction on slippery surfaces. Shifting may be harsh or delayed. Avoid towing or off-road driving until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1429 to identify the root cause.
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Quick Info
Category
Chassis
System
Transfer Case / Drivetrain
Difficulty
Type
Manufacturer
Recommended Tools
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