C1231
Speed Wheel Sensor Rear Center Circuit Open
Chassis Chassis/Safety ABS wheel speed sensor 🔴 Serious — Stop or limit driving
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What This Actually Means
In plain language — no jargon

The rear center wheel speed sensor has a broken wire or loose connection, like a phone charger that won't make contact. Without this signal, the ABS and traction control systems can't properly monitor that wheel's speed.

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Symptoms You May Notice
3 known symptoms for this code
ABS warning light illuminated
Traction control disabled or warning light on
Possible loss of stability control features
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors the rear center wheel speed sensor for an AC voltage signal that changes with wheel rotation. When the circuit is open, no signal voltage is detected, triggering a fault. The system expects continuous signal feedback to calculate wheel speed and slip conditions.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor signal voltage 0.5-5V AC (variable) No signal or continuous 0V
Signal frequency 10-300 Hz (speed dependent) Zero Hz or no frequency detected
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Wheel speed sensor connector
Inspect and reseat the connector at the rear center wheel, cleaning any corrosion.
2
Wheel speed sensor wiring harness
Check the entire wiring from wheel to ECU for breaks, pinches, or damaged insulation.
3
Wheel speed sensor
Replace the rear center wheel speed sensor if connector and wiring are intact.