What Does C1227 Mean?
The ABS module has detected that the left rear wheel speed sensor input circuit is shorted to battery voltage. Instead of receiving the expected low-voltage AC signal from the sensor, the module is seeing a constant or intermittent 12V on the signal line. This disables ABS and traction control, and the associated warning lights will be illuminated.
Common Causes
40%
Wiring harness chafed against a power source, shorting the sensor signal wire to 12V
25%
Corroded or damaged connector with pin-to-pin cross-connection to a powered circuit
15%
Aftermarket trailer wiring or accessory creating a back-feed into the sensor circuit
10%
Water-damaged ABS module connector allowing voltage bridging between pins
10%
Internal ABS module input circuit failure
Diagnostic Steps
1
Disconnect the left rear wheel speed sensor connector and measure voltage on the harness side with key on — any voltage above 1V indicates a short to battery in the harness between the sensor connector and the ABS module.
2
With the sensor disconnected, check for voltage on both signal wires at the ABS module connector end — this isolates whether the short is in the under-vehicle harness or at the module itself.
3
Inspect the left rear sensor wiring along its entire route for chafing against brake lines, fuel lines, or suspension components where it could contact 12V wiring.
4
Check for aftermarket trailer wiring or accessories near the rear axle area that may have been spliced into or run alongside the wheel speed sensor harness.
5
Inspect all connectors in the circuit for corrosion, water damage, or bent/spread pins that could bridge to adjacent powered circuits.
Estimated Repair Cost
$75 - $400
Parts + labor, varies by vehicle and location
The ABS module has detected that the left rear wheel speed sensor input circuit is shorted to battery voltage. Instead of receiving the expected low-voltage AC signal from the sensor, the module is seeing a constant or intermittent 12V on the signal line. This disables ABS and traction control, and ...
The most common cause of C1227 (Speed Wheel Sensor LR Input Short Circuit To Battery) is: Wiring harness chafed against a power source, shorting the sensor signal wire to 12V
Typical repair costs for C1227 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
ABS and traction control are disabled. Standard braking remains functional. The short to battery will not damage the sensor but prevents proper operation. Drive cautiously and avoid situations requiring ABS intervention. Safe to drive to a repair facility at moderate speeds.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1227 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Traction Control
Difficulty
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