What Does C1231 Mean?
The ABS module has detected an open circuit in the rear center wheel speed sensor wiring. There is a break in the electrical path between the sensor and the module, resulting in no signal being received. ABS and traction control are disabled with dashboard warning lights active.
Common Causes
35%
Broken or severed wire in the rear center sensor harness from road debris or vibration fatigue
25%
Disconnected or unseated connector at the sensor or an inline splice
20%
Corroded connector pins creating a high-resistance open condition
15%
Failed sensor with internal open winding
5%
ABS module connector pin pushed back or damaged
Diagnostic Steps
1
Measure resistance at the rear center sensor connector — expect 800-2000 ohms across the signal pins. An open (infinite resistance) reading confirms either a sensor failure or a break in the wiring upstream of the measurement point.
2
If the sensor reads correct resistance, move to the ABS module connector and measure resistance on the same circuit pins. An open here with good sensor resistance means the break is in the harness between the two points.
3
Perform a wiggle test on the harness while monitoring continuity with an ohmmeter — this can locate intermittent breaks caused by vibration fatigue, especially at flex points near the rear axle.
4
Inspect the harness routing for physical damage from road debris, exhaust heat, or suspension component contact. Pay attention to where the harness enters the body or crosses moving components.
5
Check connector pins at both ends for pushed-back terminals, green corrosion, or damaged locking tabs that could cause an intermittent disconnect.
Estimated Repair Cost
$50 - $300
Parts + labor, varies by vehicle and location
The ABS module has detected an open circuit in the rear center wheel speed sensor wiring. There is a break in the electrical path between the sensor and the module, resulting in no signal being received. ABS and traction control are disabled with dashboard warning lights active.
The most common cause of C1231 (Speed Wheel Sensor Rear Center Circuit Open) is: Broken or severed wire in the rear center sensor harness from road debris or vibration fatigue
Typical repair costs for C1231 range from $50 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
ABS and traction control are disabled. Conventional braking remains fully functional. This is safe to drive to a repair facility, but ABS will not activate during emergency braking. Use caution on wet or icy roads.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1231 to identify the root cause.
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Quick Info
Category
Chassis
System
ABS / Traction Control
Difficulty
Type
Manufacturer
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