What Does C1237 Mean?
The ABS control module has detected that the rear wheel speed input signal is missing during vehicle operation. This code typically applies to single-rear-axle speed sensor configurations where one sensor monitors both rear wheels. Without this signal, the ABS module cannot calculate rear axle deceleration rates for proper brake modulation.
Safety Warning
Without rear wheel speed data, ABS cannot properly modulate rear brakes. This may cause rear wheel lockup during hard braking, leading to loss of vehicle stability. Repair immediately.
Common Causes
35%
Failed rear wheel speed sensor mounted on the differential or rear axle housing
25%
Damaged wiring harness between the rear axle sensor and ABS module, especially where it routes over or near the exhaust system
20%
Worn or damaged reluctor ring inside the differential causing inconsistent or absent signal generation
15%
Corroded connector at the sensor or inline splice point from exposure to road moisture
5%
ABS module rear input channel internal failure
Diagnostic Steps
1
Step 1: Locate the rear speed sensor on the differential housing or rear axle. Inspect for physical damage, loose mounting, or contamination with gear oil from a leaking seal.
2
Step 2: Measure sensor output with DVOM on AC volts while spinning a rear wheel (vehicle safely raised). A passive sensor should produce 200-800mV AC at low speed.
3
Step 3: Check wiring continuity from the sensor connector to the ABS module connector pins. Verify no shorts to ground or to battery voltage.
4
Step 4: Inspect the reluctor/tone ring inside the differential (may require cover removal) for damage, missing teeth, or metallic debris contamination.
5
Step 5: Clear codes, test drive at 25+ mph, and verify the rear wheel speed reading matches the front wheel speeds within 1-2 mph via live data.
Estimated Repair Cost
$120 - $500
Parts + labor, varies by vehicle and location
The ABS control module has detected that the rear wheel speed input signal is missing during vehicle operation. This code typically applies to single-rear-axle speed sensor configurations where one sensor monitors both rear wheels. Without this signal, the ABS module cannot calculate rear axle decel...
The most common cause of C1237 (Speed Wheel Rear Input Signal Missing) is: Failed rear wheel speed sensor mounted on the differential or rear axle housing
Typical repair costs for C1237 range from $120 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Without rear wheel speed data, ABS cannot properly modulate rear brakes. This may cause rear wheel lockup during hard braking, leading to loss of vehicle stability. Repair immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1237 to identify the root cause.
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Quick Info
Category
Chassis
System
Anti-lock Brake System (ABS) / Traction Control System
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