What Does C1236 Mean?
The ABS control module has detected a missing input signal from the left rear wheel speed sensor. The module expects a continuous speed signal during vehicle movement but is receiving no data from this circuit. This affects ABS braking calculations and traction control intervention for the left rear wheel.
Safety Warning
ABS and traction control will not function correctly without a valid left rear wheel speed signal. This reduces braking effectiveness on slippery surfaces. Repair promptly.
Common Causes
35%
Failed left rear wheel speed sensor with no output signal due to internal coil failure or magnet degradation
25%
Severed or damaged wiring between the left rear sensor and ABS module, often from road debris or improper routing near suspension components
20%
Excessive air gap between sensor and tone ring caused by worn wheel bearing allowing lateral play
15%
Damaged or contaminated ABS tone ring with packed debris, rust, or missing teeth preventing signal generation
5%
Disconnected or corroded connector at the sensor pigtail or ABS module harness
Diagnostic Steps
1
Step 1: Check the left rear wheel speed sensor connector for proper seating, corrosion, or backed-out pins. Disconnect and inspect both halves of the connector.
2
Step 2: Measure sensor resistance (800-1400 ohms typical for passive sensor). If OL or near zero, the sensor has failed internally.
3
Step 3: Check for excessive wheel bearing play by grasping the tire at 12 and 6 o'clock and rocking. More than 0.005 inches of lateral play can cause signal loss.
4
Step 4: Inspect the tone ring for damage. Rotate the wheel slowly and look for missing teeth, cracks, or heavy corrosion through the sensor bore hole.
5
Step 5: Compare all four wheel speed sensor signals via live data at a steady 25 mph. All should read within 1-2 mph of each other. Clear codes and road test.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
The ABS control module has detected a missing input signal from the left rear wheel speed sensor. The module expects a continuous speed signal during vehicle movement but is receiving no data from this circuit. This affects ABS braking calculations and traction control intervention for the left rear...
The most common cause of C1236 (Speed Wheel LR Input Signal Missing) is: Failed left rear wheel speed sensor with no output signal due to internal coil failure or magnet degradation
Typical repair costs for C1236 range from $100 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
ABS and traction control will not function correctly without a valid left rear wheel speed signal. This reduces braking effectiveness on slippery surfaces. Repair promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1236 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
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