C0043 indicates a fault in the secondary (Circuit B) signal path of the brake pedal position sensor, which the ABS or electronic stability control module uses to detect brake application and to coordinate braking-related functions. The sensor typically outputs two redundant signals, and this code is set when Circuit B is out of range, erratic, or does not agree with the expected values. It is an ABS/chassis code rather than an engine-management code, so it will not normally affect engine power on its own.
The internal dual-track sensor can wear out or develop an open/short in the Circuit B element, causing the signal to drift out of range or fail entirely. This is the single most common root cause for this code.
An open, short-to-ground, short-to-power, or high-resistance condition in the Circuit B wiring between the sensor and the ABS/control module can set this code after repeated signal plausibility checks fail.
Poor contact at either the sensor connector or the module connector can introduce intermittent voltage drop or noise that the module interprets as a Circuit B failure.
If the sensor has been disturbed during pedal assembly or carpet work, an improper air gap or travel range can produce a signal that is outside the expected B-circuit profile.
Only after the sensor and wiring have been ruled out should the control module be considered, as internal input-circuit damage in the module is genuinely possible but far less common than the sensor itself.
No. C0043 is a brake/chassis-system code monitored by the ABS or stability-control module, not the engine computer. Replacing the PCM would not fix this code.
Normal braking is usually unaffected, but ABS, traction control, and related functions may be disabled. Have it diagnosed promptly, especially if other brake warning lights are on.
The sensor itself is the most likely cause, but wiring and connector faults are common enough that they should be tested before replacing parts.
A failed ABS module input circuit is possible, but it is much less likely than a bad sensor or wiring fault. Module replacement should only be considered after the sensor and Circuit B wiring are proven good.