C0664 indicates that the ABS control module has detected a discrepancy between the signal from the left rear wheel speed sensor (designated as sensor B) and the expected correlation with the other wheel speed sensors. This usually points to a problem with the sensor, its wiring, or the tone ring it reads.
The sensor itself may have internal failure, producing no signal or an erratic signal that does not correlate with the other wheels.
Corrosion, chafing, loose pins, or water intrusion in the sensor harness can interrupt or distort the signal.
Missing teeth, debris, or rust on the reluctor ring can cause the sensor to miss pulses, leading to a correlation fault.
Though uncommon, a fault inside the ABS control unit's signal processing circuit can generate a false correlation code.
The powertrain control module rarely causes this code; it would only be considered after all sensor, wiring, and ABS module checks are negative.
No. The PCM/ECM is almost never the cause of this wheel‑speed sensor correlation code; the sensor, its wiring, or the tone ring are far more likely culprits.
You can drive, but ABS and traction/stability control may be disabled or behave unpredictably, which can increase stopping distance and reduce stability in slippery conditions.
Generally no. Once a good sensor is installed and the wiring is intact, clearing the code and verifying normal operation is sufficient; the ABS module will learn the signal automatically.