C1429 Code: Meaning, Symptoms, Causes & Fix

Overview

C1429 is triggered when monitoring logic identifies an issue with Input-shaft-speed input circuit failure affecting ABS/chassis dynamics and brake control.

Symptoms

ABS/traction light on
longer braking intervention
reduced stability control performance

Common causes

Control module logic or calibration issue affecting input-shaft-speed input circuit failure
Component failure in the monitored system
Connector pin damage/corrosion or harness stress near related components

How to diagnose C1429

Confirm C1429 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to input-shaft-speed input circuit failure for obvious defects.
Use freeze-frame and live data to isolate whether the issue is electrical, mechanical, or control logic.
Check for related DTCs to identify the root-cause chain before replacing parts.
After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code C1429

Low: This code is low to moderate severity in most cases, but diagnosis is still recommended to avoid recurring warnings.

Can you drive with C1429?

The vehicle is often drivable with C1429, but plan a repair window to prevent repeat faults.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

Repair obvious wiring/connector faults first to prevent repeat parts replacement.
Address the root fault mode (generic) in the input-shaft-speed input circuit failure circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify C1429 remains cleared under the conditions that originally set the code.

Fix options

Test component operation and replace if faulty.
Inspect circuit and connector condition.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$120-$500

Common mistakes when diagnosing C1429

Replacing parts without verifying voltage, ground, and signal integrity first.
Ignoring related stored/pending codes that indicate upstream faults.
Skipping post-repair verification drive cycle and readiness checks.

C1429 in common vehicles

C1429 appears across makes such as BMW, Mercedes-Benz, Audi, Volvo. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes C1429?

C1429 is commonly set by generic faults affecting input-shaft-speed input circuit failure.

How much does it cost to fix C1429?

For C1429, repair costs are typically $120-$500 depending on exact root cause, labor rates, and part quality.

Can I clear C1429 without repair?

You can clear C1429 temporarily, but the code usually returns until the underlying fault is corrected.