What Does C1166 Mean?
This code indicates the ABS control module has detected an open circuit in the right rear wheel speed sensor circuit. The electrical path between the RR sensor and the ABS module is broken, resulting in complete loss of the speed signal from that wheel. This is a definitive electrical fault rather than a signal quality issue.
Safety Warning
ABS and traction control are disabled. No RR wheel speed data available. Repair promptly.
Common Causes
30%
Broken wire in the RR sensor harness from road debris impact or underbody corrosion
25%
Disconnected or backed-out connector at the sensor or at a body harness junction
25%
Failed wheel speed sensor with internally open coil winding
20%
Severely corroded terminals creating an effective open circuit
Diagnostic Steps
1
Step 1: Verify the RR sensor connector is fully seated and locked. Inspect for backed-out pins or bent terminals.
2
Step 2: Measure sensor coil resistance (800-1400 ohms typical). An OL reading means the sensor coil is open.
3
Step 3: If sensor resistance is normal, check wiring continuity from sensor to ABS module on both wires.
4
Step 4: Locate the break by testing at intermediate connectors along the harness route. Common failure points are near the rear axle and body-to-frame transition.
5
Step 5: Repair the open circuit or replace the sensor, clear codes, and road test above 15 mph.
Estimated Repair Cost
$80 - $350
Parts + labor, varies by vehicle and location
This code indicates the ABS control module has detected an open circuit in the right rear wheel speed sensor circuit. The electrical path between the RR sensor and the ABS module is broken, resulting in complete loss of the speed signal from that wheel. This is a definitive electrical fault rather t...
The most common cause of C1166 (Speed Wheel Sensor RR Input Open Circuit) is: Broken wire in the RR sensor harness from road debris impact or underbody corrosion
Typical repair costs for C1166 range from $80 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
ABS and traction control are disabled. No RR wheel speed data available. Repair promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1166 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS) / Traction Control System
Difficulty
Type
Manufacturer
Recommended Tools
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